Liquid plugs

ABSTRACT

A rotatable microfluidic device that comprises a hydrophilic microchannel structure in which there is a) an upstream microcavity I with a liquid outlet I, b) a microconduit I connected to liquid outlet I, and c) a capillary valve I associated with microconduit I. The inlet end of the microconduit is closer to the spin axis than the outlet end of the microconduit. The difference in radial distance between the inlet end and the outlet end of microconduit I is typically ≧5%, such as ≧10% or ≧100% or ≧500%, of the difference in radial distance between the uppermost part of the upstream microcavity and liquid outlet I.

The present application claims priority to PCT/SE2006/000450, filed Apr.13, 2006, which claims priority to U.S. Provisional Patent Application60/671,151, filed Apr. 14, 2005, and claims priority to U.S. ProvisionalPatent Application 60/673,180, filed Apr. 20, 2005, and claims priorityto Swedish Application No. 0501747-0, filed Jul. 29, 2005, all of whichapplications are incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a microfluidic device in which thereare one or more hydrophilic microchannel structures each of whichcomprises one or more of the innovative microfluidic functionalities orunits presented herein, and to fluidic methods or operations utilizingthese functionalities or units.

A microfluidic device of the invention has one or more microchannelstructures which each comprises at least one or more of the functionalunits of the invention:

-   -   A. Capillary valve unit that permits decreased spinning for        downstream transport of an aliquot of a liquid, once the front        of the liquid has passed the valve (kick-valve).    -   B. Capillary valve unit requiring maintained increased spinning        in order for a front of a liquid to pass the capillary valve        (upward-turn valve).    -   C. Capillary stop unit (finger valve and/or finger vent).    -   D. Protected capillary valve unit.    -   E. Unit for separating an upper phase, typically a liquid phase,        from a denser phase typically comprising particulate material.    -   F. Detection unit.        All units A-F are primarily contemplated for centrifugal-based        microfluidic devices. Units such as C, D, E, and F may also be        used in systems in which liquid flow is driven by other forces        including capillary forces.

If not otherwise apparent from the context, the terms “upper” and“higher” versus “lower”, “upward” versus “downward”, “inward” versus“outward”, “above” versus “below” etc will refer to locations inrelation to the direction of the main force used to drive liquidtransport or flow downstream within the major parts of a microchannelstructure, for instance within a major flow path. In centrifugal-basedsystems this means that a “higher” or an “upper” level/position (innerposition) is at a shorter radial distance compared to a “lower”level/position (outer position). The radial distance of a level/positionis the shortest way from the level/position concerned to a spin axisabout which the device can be spun to create centrifugal force used inthe device. Similarly, the terms “up”, “upward”, “inwards”, and “down”,“downwards”, “outwards” etc will mean towards and from, respectively,the spin axis. A “height” will be considered as the difference in radialposition or distance between two levels with the base level being theouter/lower level.

The terms discussed in the preceding paragraph are not to be mixed upwith the terms “upstream” or “downstream” that solely refer to the orderin which various functional units appear in a flow path and/or the orderthe various steps of a protocol are carried out. In other wordsdownstream means “after” and upstream “before”.

A hydrophilic microchannel structure comprises a system of one or moremicroconduits/microchannels and/or microcavities that arehydrophilic/wettable in the sense that once a liquid front of a liquid,primarily aqueous, has started to pass a valve function or an inletopening within the structure, the liquid will further penetrate thesystem by self-suction or capillary force (passively) unless hindered bya valve function and/or vent or by a counter-pressure, for instancecreated by air in a non-vented interior area, or by other means. Thehydrophilicity downstream a valve function is typically such thatpassive liquid transport can be resumed, if desired, after the liquidfront has passed the valve. The principle of self-suction in particularapplies to the innovative units described herein and to structures/unitsthat are in a dry state. The microchannel structure may also containmicroconduits/microchannels that are not intended for liquid transport.These latter microconduits/microchannels are typically hydrophobic atleast at their connection to a hydrophilic part of the structure that isintended for transport of liquid.

That two parts of a microchannel structure is in fluid or liquidcommunication with each other means that liquid is intended to betransported between them.

All patent and patent applications cited in the specification are herebyincorporated in their entirely by reference.

BACKGROUND TECHNOLOGY

Capillary valves have turned out to be useful for controlling liquidtransport in centrifugal-based microfluidic devices. One of the mainadvantages has been that neither this kind of valves nor centrifugalforce requires mechanical means on-board a microfluidic device.Capillary valves are stops for a liquid flow/transport and are not to beconfused with flow restrictions that permit flow but reduce the flowrates (impede flow). Once a liquid front is breaking through a capillaryvalve there is in principle no hinder for the ongoing flow or forrestarting after a stop (as long as contact with liquid is maintained).

The use of capillary or surface tension stop functions in the form ofvalves, vents, anti-wicking means etc in centrifugal-based microfluidicsystems has been described by Gamera Biosciences and Gyros AB, amongothers: WO 9853311, WO 0078455, WO 0187486, WO 0079285; WO 0187487; WO2004058406; WO 9807019 (all of Tecan Trading/Gamera Biosciences) and WO9958245; WO 0040750; WO 0147638; WO 0185602; WO 0274438; WO 0275312; WO03018198; WO 03024598; WO 04103890; WO 04103891; etc (all of Gyros AB).

According to the Gamera/Tecan publications an increase incross-sectional dimension to obtain a capillary valve in a hydrophilicmicrochannel could be anything from continuous to abrupt. Our work withmicrofluidic devices has primarily dealt with devices replicated inplastic material. It is our experience that capillary valving based onincreases in cross-sectional dimensions requires extremely sharp anddistinct changes of a kind not recognized in WO 9807019. Conventionalembossing, injection moulding etc and other replication techniques thusseem insufficient for the manufacture of microfluidic valves based on achange in cross-sectional dimension. In order to distinguish changesthat create a valving effect from other changes the former will becalled “sharp” increases/changes compared to other changes that have noor only an insignificant valving effect.

Another centrifugal based approach is given by the company Abaxis. Seefor instance U.S. Pat. No. 5,186,844, U.S. Pat. No. 5,242,606, U.S. Pat.Nos. 5,693,233, 5,160,702 etc and J. Autom. Chem. 17(3) (1995) 99-104(Schembri et al). In Abaxis' system the flow resistance in a channelgoing between the reservoirs controls the flow between an innerreservoir and an outer reservoir. Compare also U.S. Pat. No. 6,632,656(Gyros AB). In some instances the flow between an inner and an outerreservoir is controlled by so called siphons, i.e. the channel concernedis of capillary dimensions starts from the inner reservoir by making aninward turn (elbow) before ending in the outer reservoir. At asufficiently high spin speed centrifugal force will prevent liquid frompassing over the extreme of the elbow. When the spin speed is sloweddown and/or stopped wicking starts transporting liquid over the extreme.Resumed spinning further supports this liquid transport. An innerreservoir may be designed as a separation unit for separating offsuspended particulate material, such as cells, from a liquid, such asblood. In order to safely retain the particulate material in thereservoir the bottom of the of the reservoir has weirs delineating theouter part from the inner part of the reservoir such that theparticulate material will be maintained in the outer part even whenspinning is decreased or stopped. Mixing can be accomplished in mixingchambers containing two different aliquots by cycles of forward andreversed spinning or of accelerated and decelerated spinning.

In conclusion:

-   -   Gyros' system primarily contemplates processing nl-aliquots of        liquid containing reagents by the use of centrifugal force        and/or capillary force in hydrophilic microconduits. Starting        aliquots containing an uncharacterized entity, e.g. an analyte,        may be in the μl-range, such as ≦30 μl or ≦20 μl. Earth's        gravity is as a rule not of interest.    -   Abaxis' system utilizes considerably larger volumes and        dimensions, together with centrifugal force and gravity. The        wettability of the channels and capillary force is of minor        interest (except for the siphons discussed above). Starting        aliquots containing an uncharacterized entity and reagent        aliquots are typically well above the nl-range, such as ≧10 μl        or ≧30 μl or ≧30 μl. In many cases the channels are large enough        to permit entrance of liquid into non-vented reservoirs without        risk for inclusion of air bubbles (filling and venting in        parallel through the same channel).    -   Tecan's system is intermediary to Gyros' and Abaxis' systems.

OBJECTS OF THE VARIOUS ASPECTS OF THE INVENTION

Unit A: Technical problems and/or advantages: There is often a need incentrifugal-based system to link two capillary valves (I and II) inseries such that a liquid passing through an upper capillary valve Ishall be collected at a lower capillary valve II. Collection of liquidat valve II will mean that a liquid plug height will be built up whichin turn means that the risk for the liquid to leak through valve II willincrease while liquid is being collected at this valve. Risks foruncontrolled flow through are also at hand for other through-flowfunctional units that require a controlled flow and are presentdownstream of an upper valve I. A typical example is a reactionmicrocavity containing a solid phase (e.g. porous bed) with animmobilized reactant that is to be reacted under flow conditions with areactant dissolved in a liquid entering the microcavity from valve I.

We have managed to lower these risks by placing valve I in amicroconduit I that has an inlet end at a higher level than its outletend in combination with designing the microconduit to support formationof a liquid plug that extends continuously downstream from valve I to aliquid front that is within microconduit I and at a lower level than theinlet end. The creation of a positive plug height between the liquidfront and the inlet end will support and facilitate downstream transportof liquid. As a consequence the spin speed for transport of liquid froman upstream microcavity I having a liquid outlet I connected to theinlet end of microconduit I can be reduced with a concomitant reductionof the risk for undesired flow through of a valve (=valve II) or adownstream porous bed.

We have also recognized that additional positive effects can be achievedif unit A is linked to or comprises one or more characteristic featuresof at least one of the functional units B-F.

Unit B: Technical problems and/or advantages: It would be beneficial tohave a simple method for the manufacture of a capillary valve for whichthe spin speed/centrifugal force for break-through of liquid flow easilycould be varied in a predetermined manner during the manufacture. Thesolution to this problem is to place the capillary valve in an upwardlydirected segment of a microconduit that in the upstream direction is inliquid communication with a microcavity containing a liquid, the upperlevel of which is above or at about the same level as the uppermostlevel of the microconduit. The centrifugal force/spin speed required forliquid to break through the valve will depend on the level of the valverelative to the spin axis. A valve placed at a higher level in theupwardly directed segment will require a higher spin speed compared to avalve placed at a lower level.

We have also realized that further advantages can be accomplished ifunit B also is linked to or comprises one or more characteristicfeatures of at least one of the functional units A and C −F.

Unit C: Technical problems and/or advantages: We have recognized thatcreation of a liquid plug in a downwardly directed hydrophilicmicroconduit after liquid has passed a capillary valve in themicroconduit is associated with problems. Air bubbles will easily beincluded, surface transport (wicking) may be quicker than plugtransport, etc. We have accomplished to minimize these problems bylocally dividing the microconduit at the valve position in two or moremicrochannels (=fingers) with the aim to increase the available amountof liquid per time unit for plug formation. At both sides of the stopfunction/valve function, the microchannels start from or exit into aspace that is common for all of them. At least two of the microchannelsare functionally equal in the sense that the liquid front breaks throughthem in parallel as defined elsewhere in this specification. Furtherimprovements may be accomplished if it is secured that the sum of thecross-sectional areas of the microchannels are lower than thecross-sectional area of the microconduit downstream of themicrochannels. We have also realized that similar designs also arefavourable as vent functions to level out overpressure/subpressurecreated in microfluidic devices during their use.

We have also realized that further improvements can be accomplished ifthis unit linked to or comprises one or more characteristic features ofat least one of the functional units A-B and D-F.

Unit D: Technical problems and/or advantages: The efficiency of acapillary valve may have a tendency to go down when contacted withliquids that contains materials that can negatively affect this kind ofvalves, e.g. surface active materials and materials that can precipitatein and/or clog microchannels. Finger valves as defined for unit C may beparticular prone to clogging. Therefore it may be advantageous toprotect capillary valves from unnecessary contact with this kind ofliquids.

We have accomplished this kind of protection by introducing anadditional capillary valve function in the same microconduit as thecapillary valve to be protected. The additional valve is upstream of thevalve to be protected.

We have also realized that further improvements can be accomplished ifunit D is linked to or comprises one or more characteristic features ofat least one of the functional units A-C and E-F.

Unit E: Technical problems and/or advantages: This unit comprises aseparation microcavity I in which a liquid containing denser materialand lighter material is separated by centrifugation to obtain a phasesystem comprising a lower phase and an upper phase. The denser materialwill partition to the lower phase. It may be particles like cells andsolid phases in the form of particles and other particulate materialsthat are suspensible in the liquid phase and have a larger density thanthe liquid phase. The lighter material will partition to the upper phaseand is typically a liquid phase containing dissolved material, i.e.particle-depleted liquid such as plasma, supernatants from cell culture,cell homogenates, tissue homogenats and from other biologically derivedfluids containing particulate material. See for instance WO 2002074438(Gyros AB), WO 9853311 (Tecan Trading/Gamera Biosciences), US20040121449 (Bayer Healthcare), U.S. Pat. No. 5,186,844, U.S. Pat. No.5,242,606, U.S. Pat. No. 5,693,233 etc (Abaxis), and J. Autom. Chem.17(3) (1995) 99-104 (Schembri et al). After centrifugation, the upperphase is transferred via a liquid outlet I on the separation microcavityand an outlet microconduit I to a separate microcavity II in whichfurther processing is taking place. WO 2002074438 (Gyros AB) suggeststhat microconduit I shall be directed slightly outwards at itsconnection to the separation microcavity with a capillary valve in theform of a hydrophobic break directly associated with the connection. WO9853311 (Gamera Biosciences) suggests two variants for selectivelytransporting an upper plasma phase to a separate microcavity II: a) aclosing valve (wax valve, FIG. 9), or a variant in which the upperplasma level is adjustable upwards after formation of the phase system(FIG. 10). US 20040121449 (Bayer Healthcare) suggests a downwardlydirected outlet microconduit containing a hydrophilic or a hydrophobicstop. Abaxis with their larger volumes suggests that the outletmicroconduit I for the upper phase may be directed among otherstangentially or inwards/upwards (U.S. Pat. No. 5,186,844, U.S. Pat. No.5,242,606, U.S. Pat. No. 5,693,233 etc, and J. Autom. Chem. 17(3) (1995)99-104 (Schembri et al)).

We have recognized that improvements are required for microfluidicseparation units in order to

-   a) prepare particle-depleted fractions of sufficiently high quality,-   b) integrate preparation of particle-depleted liquids with accurate    metering and/or further processing in microfluidic devices, and/or    Lowering of the amount of particles in liquids initially containing    suspended particles typically requires high g-forces/spin speeds and    high risks for malfunctioning of valves and other through-flow    functional units that might be present downstream a separation unit    in a microfluidic device. Malfunctioning includes among others    precipitation and/or clogging of finger valves, porous beds, narrow    microconduits etc. See the discussion above for unit A.

We have realized that improvements can be accomplished in the casemicroconduit I connected to liquid outlet I comprises an upward segmentnext to liquid outlet I, preferably with a capillary valve I beingassociated with this segment. This means that liquid outlet I withpreference should be placed in an upwardly directed part of the innerwall of microcavity I. In other words the transport direction throughliquid outlet I should be upwards. According to our innovative conceptadvantages may also be achieved for other transport directions throughliquid outlet I. The capillary valve may be directly associated withliquid outlet I and is preferably a finger valve.

We have also realized that further improvements can be accomplished ifunit D is linked to or comprises one or more characteristic features ofat least one of the functional units A-C and E-F.

Unit F: Technical problems and/or advantages: Microfluidic detectionmicrocavities in which a result of a reaction taking place in anupstream reaction microcavity is read in a solution have typically beenin the form of a microconduit or a chamber. In many cases the detectionmicrocavity contains a liquid that is displaced by the solution comingfrom the reaction microcavity and containing molecular entitiesreflecting the result. In conventional types of microfluidic detectionmicrocavities this kind of design typically means a significant risk forthe incoming solution to mix with the liquid that preoccupies thedetection microcavity. This adverse effect has in particular been founddisturbing in centrifugal based systems. Mixing at this stage is notdesirable because it will lower the concentrations of the entities to bedetected/measured.

We have now recognized a way to lower this kind of undesired mixingwhich is suitable for centrifugal-based microfluidic devices. Ourproposal is to design the detection microcavity as a microconduit thathas an inlet part, an outlet part, and between these two parts definesone or more vertical meanders each of which comprises at least tworeturns. The section between two returns is called an intermediarysection and a return between the first and the last return is called anintermediary return. The meander may be directed upwards with the mainflow direction being upwards, i.e. the inlet part is at a lower levelthan the outlet part (upward meander). The meander may alternatively bedirected downwards with the main flow direction being downwards, i.e.the inlet part is at a higher level than the outlet part (downwardmeander).

Microconduits comprising lying meanders and used as distributionmanifolds have been described in WO 02074438, WO 02075312, WO 03093802;WO 03018198; WO 03024598; WO 0450247; WO 04083108; WO 04083109; and WO04106926 (all of Gyros AB). Microconduits comprising standing meandersand used as mixing microconduits have been described in WO 00078455; WO00079285; and WO 01087487 (all of Gamera Biosciences/Tecan Trading).According to WO 01087487, measurements and/or performing reactions canalso be carried out in a meandering mixing microconduit.

THE INVENTION

The present invention is a microfluidic device of the type generallydescribed under the headings Technical Field and General aboutMicrofluidic Devices. The characteristic feature of the device is thatat least one, two or more of the microchannel structures of the devicecomprise at least one of the functional units A-F with the features asdescribed in this specification.

For each unit there is also a corresponding innovative method comprisingthe use of the device and/or a microchannel structure and/or afunctional unit of the present invention for transporting and/orprocessing one or more aliquots of liquid. At least one of the aliquotscontains a reactant of a preparative, synthetic or analytical processprotocol. This reactant may be an uncharacterized entity (analyte) or areagent contained in a sample (aliquot) to be processed. The protocolsare typical within the field of chemistry, biology, medicine etc

A microconduit, such as microconduit I or II in the various inventiveunits, is a part of a microchannel structure and comprises one inlet endand one outlet end. If not otherwise specified a microconduit isintended for transport of one or more aliquots of liquid that may or maynot contain one or more of the above-mentioned reactants. Between theinlet end and the outlet end of a liquid transport microconduit theremay be a capillary stop function in the form of a capillary valve orcapillary vent, but no distinct microcavities (unless they are usedsolely for defining a capillary valve or vent) and no branchingsinvolving other liquid transport microconduits. One or more ventmicroconduits may be connected to a liquid transport microconduit. Ifnot otherwise specified a vent microconduit is solely used for transportof air/gas in order to level out overpressure or subpressure that mightbe created within the microchannel structure during the transport and/orprocessing of liquids. Between the ends of a vent microconduit there maybe a microcavity.

An inlet end of a microconduit that is directly connected to a liquidoutlet of a microcavity includes that the end and the outlet arecoinciding. Thus a valve or a vent that is placed in or at amicroconduit inlet end that is directly connected to a liquid outlet ofa microcavity is also placed in or at the liquid outlet. Similarly alsoapplies for the outlet end of a microconduit that is directly attachedto the liquid inlet of a microcavity.

The position of a stop capillary valve shall be considered to be theposition at which the front meniscus stops.

Non-closing valves such as capillary valves also comprise a ventfunction.

A. Unit Supporting Downstream Transport from a Capillary Valve byCreation of a Driving Liquid Plug

This functional unit comprises:

-   -   a) an upstream microcavity I (4) with a liquid inlet I (5) and a        liquid outlet I (6),    -   b) a microconduit I (17) that has an inlet end (16) and an        outlet end (18), and    -   c) a capillary valve I (24) that is associated with microconduit        I (17).

The upstream microcavity (4) is intended for retaining a liquid aliquotwhich defines an upper liquid level I in the microcavity. This upperliquid level is equal to or lower than the level of the uppermost partof the microcavity (4) (typically at the level of liquid inlet I (5))and also above the level of liquid outlet I (6).

The device (1) and the microchannel structure (2) containing the unit aswell as the unit itself are designed to permit spinning about a spinaxis (3) in order to drive liquid placed in the upstream microcavity (4)to exit the microcavity via liquid outlet I (6) and further downstreamvia microconduit I (17). The transport primarily is caused bycentrifugal force created by the spinning and/or by hydrostatic pressurebuilt up in the individual microchannel structures during spinningand/or by capillary force. Capillary force sufficient to causeself-suction may be used as a supplement when the spinning and/orhydrostatic pressure are/is insufficient for the transport, for instanceduring non- or low-spinning conditions and in particular when a liquidaliquot or at least its front meniscus shall be brought to a positioncloser to the spin axis (3) and/or from a liquid inlet port (9,51,52,53)to the first valve or vent (15 a,15 b,24 or 25 for 9; 54,57 for 51; 55for 52; 56,58 for 53) of a microchannel structure (1) (port (9,51,52,53)opening in the surface of the device).

The main characteristic feature is that

-   i) liquid outlet I (6), i.e. also the inlet end (16) of microconduit    I (17), is closer to the spin axis (3) than the outlet end (18) of    microconduit I, and-   ii) capillary valve I (24) is placed a) at liquid outlet I (6),    or b) between the inlet and the outlet ends (16 and 18,    respectively) of microconduit I (17), and-   iii) the difference in radial distance between liquid outlet (6) of    the upstream microcavity (4) or valve I (24) and the outlet end (18)    of microconduit I (17) is typically ≧5%, such as ≧10% or ≧50% or    ≧100% or ≧200% or ≧500%, of the difference in radial distance    between the uppermost part (7) of the upstream microcavity (4) and    liquid outlet I (6) or valve I (24), such as of the difference in    radial distance between upper liquid level I and liquid outlet I (6)    or valve I (24).    The upper liquid level I is always equal or lower than the level of    the uppermost part (7) of the microcavity (4).

The part of microconduit I (17) that is downstream of valve I (24) isdesigned to be capable of supporting liquid transport as a continuousliquid plug extending from the inlet end (16) of microconduit I (17)(and also from valve I (24)) to a liquid front (front meniscus) that iswithin the microconduit (17) and also below the level of the inlet end(16) of the microconduit (17). The upper liquid level I at the start ofthe transport then corresponds to the rear meniscus which initially ismoving downwards in the upstream microcavity (4) and thenupwards/downwards in microconduit I (17) depending on it's the shape ofthe microconduit. The maximal height of this plug is equal to thedifference in radial positions of the inlet end (16) and the outlet end(18) of microconduit I (17), but in practice will depend on a number offactors such as cross-dimensions of the microconduit, kind of liquid,flow rate etc. Once the meniscus has passed valve I (24) and an upperextreme (22) (if present), the plug will grow downwardly permitting alowering of the spin speed. The requirements for obtaining this kind ofplug transport depends on a number of factors such as: dimension,position and shape of the upstream microcavity, microconduit I, and theliquid outlet of the microcavity; surface tension of the liquid; appliedcentrifugal force, kind of capillary valve including dimensions;wettability of inner surfaces in the upstream microcavity and inmicroconduit I; etc. Optimal combinations of numerical values of variousfeatures are represented in the drawings and in other parts of thisspecification. A widening of the microconduit and/or at its outlet end(18) counteracts liquid plug extension. Experimental testing is requiredin each particular case. See the experimental part.

Liquid inlet I (5) is typically in the top (7) of the upstreammicrocavity (4) and directly connected to an inlet microconduit (8 a)that in the upstream direction communicates with a liquid inlet port(5), i.e. with an opening in the surface of the device for introductionof liquid. The inlet microconduit (8 a) preferably has an overflowopening (10) at the same level as liquid inlet I (5). The overflowopening (10), if present, defines the top or uppermost part (7) of theupstream microcavity (4). See further below.

Liquid inlet I (5) is typically at a position above the level of liquidoutlet I (6). If not, then the unit contains appropriate valving forpreventing back-flow through liquid inlet I after the upstreammicrocavity has been filled to a desired level (=upper liquid level I).

The upstream microcavity has an inherent vent function in liquid outletI (6) in the case valve I (24) is a non-closing valve such as a passivevalve. There may also be one or more additional vent functions in theupstream microcavity for hindering undesired air bubble formation withinthe microcavity (not shown in drawings). These other vent functions maybe associated with a pure gas vent or an additional inlet for liquid.See below.

The liquid flow starting to exit through liquid outlet I (6) may havevarious directions in relation to the centrifugal force at the liquidoutlet I (6). The flow direction may thus comprise (a) adownward/outward component (outward radial component), or (b) anupward/inward component (inward radial component), or (c) essentiallytangential (horizontal). The flow direction relative to the direction ofthe centrifugal force at liquid outlet I (6) may thus be for alternative(a) at least partially in the same direction (along) as the centrifugalforce, for alternative (b) at least partially against the centrifugalforce, and for alternative (c) essentially orthogonal to the centrifugalforce. Expressed as an angle (α) relative to the direction ofcentrifugal force at liquid outlet I this may be for alternative (a)0°≦α≦90° such as 0°≦α≦85° (along), for alternative (b) 90°≦α≦180°, suchas 95°≦α≦180° (against), and for alternative (c) 80°≦α≦100°, such as85°≦α≦95°, and in particular 90° (orthogonal).

The angle (α′) between the centrifugal force at liquid outlet I and theinner wall around liquid outlet I and/or the opening as such may be foralternative (a) 0°≦α′≦90°, such as 10°≦α′≦90°, for alternative (b)0≦α′≦90°, such as 10°≦α′≦90° and for alternative (c) 0°≦α′≦10°, such as0°≦α′≦5° or in particular α′=0°. These intervals refer to the angle seenfrom the interior of the microcavity and regarded downward/upward.

The part of microconduit I (17) that is next to liquid outlet I (6) ofthe upstream microcavity (4) preferably has a direction selected amongstthe main directions for flow through this liquid outlet (6) although thetwo directions do not need to be the same

Microconduit I (17) may be directed continuously downwards, for instancea) be straight and coincide with or angled relative to a straight line(radius) going from the spin axis to liquid outlet I/inlet end (6/16) ofmicroconduit I (17), or b) contain a curvature, such as in a meander orin single curved variants like in evolvents. Alternatively microconduitI (17) may contain one or more upwardly and one or more downwardlydirected sections (23 a and b, respectively) between which there may beupward or downward turns (“elbows”) and/or horizontal sections.

In certain variants, microconduit I (17) comprises one upward turn thathas an upper extreme (“elbow”) (22) that is at an intermediary levelbetween the level of liquid outlet I (6) and the uppermost part (7) ofthe upstream microcavity (4), typically between the level of liquidoutlet I (6) and upper liquid level I. In other preferred variants, thelevel of the upper extreme (22) may be above or equal to upper liquidlevel I, e.g. above or equal to the level of the uppermost part (7) ofthe upstream microcavity (4). All parts of microconduit I (17) betweenthe inlet end (16) and the upper extreme (22) in the variants of thisparagraph are preferably above the level of liquid outlet I (6),typically as a microconduit section (23 a) that is continuously directedupwards. Similarly the parts (23 b) of microconduit I (17) that arebetween the upper extreme (22) and the outlet end (18) are preferablydirected continuously downwards.

Downwardly directed sections, upwardly directed sections, horizontalsections, upward turns, downward turns etc may be as described for unitsB and C and/or for the corresponding use aspects.

Capillary valve I (22) is typically positioned a) at the inlet end (16)of microconduit I (17) (coincides with liquid outlet I (6)), or b)between the inlet and the outlet ends (16,18) of microconduit I (17), orc) at the outlet end (18) of microconduit I (17).

Valve I (24) may be located either before or after an upper extreme(22). If microconduit I (17) is a single downward section, valve I (24)is at the level of the inlet end (16) of microconduit I (17) (=level ofliquid outlet I (6)) or below this level. If microconduit I (17) is anupward turn with an upper extreme (22), valve I (24) is preferablyplaced in the upward section (23 a) of the turn at a height as discussedfor unit E. Valve I (24) may also be placed in the downward section (23b). In the case the upper extreme (22) is above the level of upperliquid level I or above the level of the uppermost part (7) of theupstream microcavity (4), valve I (24) is preferably placed below therelevant ones of these levels or alternatively sufficient hydrostaticpressure is created by adding extra liquid on the rear meniscus in theupstream microcavity (4) when the unit is in use. Valve I (24) istypically placed at a level relative to liquid outlet I (6) that isabove 25% of the height between the inlet end (16) (=liquid outlet I (6)and the upper extreme (22), e.g. as part of an upward section (23 a) ofan upward turn (elbow) of microconduit I (17). The preferred relativeposition of the valve within this interval is preferably even higher,such as above 50% or above 75% of the height between inlet end (16) andthe upper extreme (22). See also units B, C and E and the use aspect ofunit A-C and E in which also other relative positions are given.

Capillary valves in the unit, such as valve I (24), are typically basedon a change in chemical and/or geometric inner surface characteristicsaccording to principles that are well-known in the field. The change maybe as a sharp increase or decrease in a cross-sectional dimension of amicroconduit (lateral change) and/or a sharp increase in non-wettabilityof an inner surface of a hydrophilic microconduit, in both cases in theflow direction. The change is typical local (break), for instance anon-wettable/hydrophobic surface break in an otherwise hydrophilic flowpath. See “General about Microfluidic Devices” and Background Technologyand publications referenced therein. Valve I (24) is preferably a fingervalve as defined in this specification in the context of units C and E.

Microconduit I (17) may contain an additional capillary valve (25)upstream of valve I (24) provided valve I is placed in the microconduitand in particular if valve I is a finger valve. See further unit D. Forvariants where the upstream microcavity is a separation microcavity asdescribed for unit E this kind of extra valve (25) may reduce the riskfor contamination and/or clogging of valve I (24) by material that is tobe separated from the liquid phase intended to pass through microconduitI. See units D and E.

The cross-sectional area in the upstream microcavity (4) is preferablylarger upstream of liquid outlet I (6) than in microconduit I (17), e.g.with a factor ≧1, such as ≧2 or ≧5 or ≧10. The cross-sectional area ofmicroconduit I upstream of valve I is preferably larger than downstreamof the valve with a factor e.g. ≧1, such as ≧2 or ≧5 or ≧10. Theselatter intervals in particular apply if valve I is a capillary stopfunction in the form of a finger valve, such as described in unit C.

Liquid outlet I (6) may divide the upstream microcavity (4) in a lowerpart (4 b) and an upper part (4 a) as discussed for unit E below, inparticular if the microcavity (4) is to be used for the separation ofdenser material from lighter material that are present in a liquid. Intypical cases the lower part (4 b) then constitutes ≧10%, such as ≧25%or ≧50% or ≧70% or ≧80% of the total volume of the upstream microcavity(4). The exact relative volumes of the parts is determined by therelative volume of the phase to be exported through liquid outlet. Seeunit E.

The upstream microcavity is typically tapered towards the level ofliquid outlet I (6) (or towards the outlet (6) as such), thus having asmaller cross-sectional area at this level compared to the largestcross-sectional area upstream of liquid outlet I (6). In the case theupstream microcavity (4) is divided into an upper and lower part (4 a,4b), there is typically a constriction of the microcavity (4) definingthe upper part (4 a) and the lower part (4 b). The constriction is thenessentially at the same level as liquid outlet I (6) and typicallydefined by tapering the upper and/or lower part towards this level. Thetapering/constriction in this variant means that the cross-sectionalarea at liquid outlet I (6) is smaller than the largest cross-sectionalarea of one or both of the parts, preferably of the upper part (4 a).Tapering may also be towards liquid inlet I (5). Se further below andthe description of unit E.

The lower part (4 b) (if present) is typically communicating with one ormore outlets (14) to ambient atmosphere solely for venting out airdisplaced by liquid entering this part (4 b). The opening (port) (14) inthe surface of the device for an outlet of this kind is preferablylocated at a higher level than the level of a liquid inlet (5) of theupstream microcavity (4) and typically also at a higher level than thelevel of corresponding inlet port (9) for the same microcavity. Theremay be a capillary stop function (downstream end) (15 a) associated withthis kind of outlet(s) (14), in particular if the corresponding openingin the surface of the device is at a lower position than the level ofliquid inlet of the upstream microcavity. The upper part (4 a) of theupstream microcavity (4) may be used as a volume-metering microcavity.See below. This metering is likely to be more accurate if the capillarystop function (15 a) associated with a vent function of the lower part(4 b) is placed at a lower level than liquid outlet I (6). See also unitD for further details.

The lower part (4 b) (if present) may also have a separate liquid outletI′ (not shown) for export of material from the lower part after theupper part has been emptied via liquid outlet I. In this case liquidoutlet I′ is at a lower level than liquid outlet I.

A capillary stop function (15 a) associated an outlet for the lower part(4 b) is preferably non-closing, e.g. in the form of a capillary valveor a capillary vent (preferably a finger vent as described for unit C).Compare WO 02074438 (Gyros AB), for instance unit 12 therein.

The total volume of the upstream microcavity (4) is the maximal liquidvolume that can be retained between the level of the uppermost part (7)(typically liquid inlet I (5)) and the level of the lowest part,typically the level of liquid outlet I (6).

Functional unit A may also comprise a downstream microcavity II (20)with a liquid inlet II (21) that is in fluid communication with theoutlet end (16) of microconduit I (17). This microcavity (20) typicallyalso has one or more outlets, for instance

-   -   a) a liquid outlet arrangement II which comprises a liquid        outlet II (32) of microcavity II (20) and an outlet microconduit        II (35) and in which transport of material out of the        microcavity is controlled, and/or    -   b) one or more vent functions.        The transport controlling function of arrangement II is        typically achieved by placing a constriction (33) at liquid        outlet II (32) that prevents particulate material, such as the        particles of packed porous bed, from escaping microcavity II        (20) and/or by including liquid flow restrictions in the        arrangement and/or a valve II, typically a capillary valve.        Valve II is typically placed in microconduit II (35), typically        at liquid outlet II (32). Flow restrictions in the form of a        porous bed (34) may be placed in the microcavity, preferably at        its outlet end (WO 02075312 Gyros AB). Flow restrictions may        also be inherent in the design of microconduit II (35), i.e. the        microconduit is long and/or narrow (WO 03024598 Gyros AB) and/or        by including other characteristics that support impeded flow,        such as rough inner surfaces, porous plugs, pillars, etc. The        downstream microcavity (20) may also have one or more additional        liquid inlets (51,52,53) that may or may not coincide with one        or more of the vent functions. Each of one, two or more of these        extra inlets may or may not be part of an inlet arrangement that        is individual for one single microchannel structure or common        for several microchannel structures and providing a        volume-defining unit with a volume-metering microcavity per        microchannel structure as described in General about        Microfluidic Devices further below.

Liquid outlet II (32) is typically placed at the lowest part of thedownstream microcavity (20) but may also be located at an intermediarylevel between the levels of lowest and the uppermost part therebydividing the downstream microcavity in an upper part and a lower part.In the latter variant the lower part may comprise a separate liquidoutlet II′ comprising a valve II′. The design of the liquid inlets,liquid outlets, valves, upper and lower parts etc of the downstreammicrocavity may be as discussed above for the upstream microcavity.

Liquid inlet II (21) is typically closer to the spin axis (3) than anyof liquid outlets II (32) and II′ (if present).

Liquid outlet II (32) may be in downstream liquid communication with adetection unit, for instance as defined for unit F below. Between thisliquid outlet there may be a microconduit II (35) as defined above.

Valve II and possibly also valve II′, if present, are preferablypassive, as discussed above and in General about Microfluidic devices,Background Technology and in publications referenced in these parts.Other types of non-closing valves may also be used. One or more of thevalves that are associated with liquid outlets on the downstreammicrocavity (20) may be finger valves as described for unit C.

Flow restrictions in the form of a porous bed (34) are typicallyassociated with the lowest of the liquid outlets (32) of the downstreammicrocavity (20). This kind of bed is typically used as a solid phasethat will interact with reactants or contaminants that are present in aliquid aliquot passing through the bed. The bed is typically in the formof a porous monolithic plug or as a packed bed of porous or non-porousparticles. The interaction with reactants and contaminants is typicallyvia a reactant that is immobilized to the solid phase material of thebed. Other kinds of flow restrictions are typically used to give acontrolled flow rate through the microcavity (20) including also througha porous bed placed therein. This will enable controlled residence timesunder flow conditions for liquid aliquots passing through themicrocavity and thus also for controlled contact times between reactantsimmobilized in the microcavity (to walls, porous beds etc) andthrough-passing reactants (WO 02075312 (Gyros AB) and WO 03024598 (GyrosAB)). The term “controlled residence time” includes that the residencetime is essentially equal for the corresponding microcavity in two ormore microchannel structures (same device) that are used simultaneouslyin the same meaning as discussed in WO 02075312 and WO 03024598.

The difference in radial distance between the inlet end (16) and theoutlet end (18) of microconduit I (17) is preferably ≧100%, such as≧200% or ≧500% or ≧1000%, of

-   -   a) the difference in radial distance between liquid inlet II        (21) and the lowest liquid outlet (32) or capillary valve or        flow restriction that is associated with the downstream        microcavity (20), or    -   b) the difference in radial distance between the upper liquid        level in the downstream microcavity and the lowest liquid outlet        valve (32) or capillary valve or flow restriction that is        associated with the downstream microcavity (20).        This does not exclude that the difference in radial distance        between the inlet end (16) and the outlet end (18) of        microconduit I (17) may be less than the difference defined        in (a) or (b) for instance ≧10%, such as ≧25% or ≧50% or ≧75%.        The term “upper liquid level” (=upper liquid level II) in (b)        refers to the liquid level in the downstream microcavity (20)        after a desired volume of liquid has been transported from the        upstream microcavity (4) to the downstream microcavity (20).

The volume of the downstream microcavity (20) beneath its half heightmay be ≧50%, such as ≧60% or ≧75%, of the total volume of themicrocavity.

In the same manner as upstream microcavity (4) the downstreammicrocavity (20) may be constricted and/or tapered.

Tapering for both microcavities (4,20) typically means that at leastone, two or more of the inner walls at the outlet/inlet concerned forman acute angle (β<90°) with the (main) transport direction through thetapering. This angle (β) preferably is in the interval of 10°-50°, suchas 20°-40° or 25°-35° with preference for about 30°. These intervals areapplicable also to pure vent outlets. With respect to liquid outlets andpure vent outlets tapering will counteract air bubble formation duringfilling of the microcavity with liquid.

If a microcavity (4,20) has a constriction and/or tapering associatedwith an inlet/outlet (5/6,32), the largest cross-sectional area of themicrocavity or an upper part (4 a) and/or lower part (4 b) thereof istypically larger than the cross-sectional area at the level ofoutlet/inlet concerned with a factor ≧1, such as ≧1.25 or ≧1.5 or ≧3.0or ≧5.0.

The upper part (if present) of the upstream microcavity (4) and/or ofthe downstream microcavity (20) may be part of a volume-defining unit,for instance of the type outlined in WO 02074438 and WO 03018198 (bothof Gyros AB).

For an upstream microcavity (4) the preceding paragraph typically meansthat the inlet microconduit (8 a) has an overflow opening (10) at thesame level as the level of liquid inlet I (5). This overflow opening(10) is typically connected to a downwardly directed overflow (11)microconduit that may end above or below the levels of valves (15 a, 15b,24,25) that may be associated with liquid outlet(s) (6,14) of theupstream microcavity (4). The uppermost portion of the upstreammicrocavity (4) is preferably constricted at and/or tapered towards thelevel of the overflow opening (10), i.e. also at and/or towards thelevel of liquid inlet I (5). See also WO 02074438 and WO 02018198 (bothof Gyros AB).

The downstream microcavity (20) may also comprise a volume-definingfunction (not shown). This typically means that the microcavity has:

-   -   a) a first liquid outlet that is an overflow opening and divides        the microcavity in an upper part and a lower part with a first        outlet microconduit that is designed as an overflow microconduit        that is directly connected to the overflow opening and directed        downwardly with its outlet end and a first valve that may be        above or below the levels of liquid outlets and/or valves of the        lower part of the microcavity, and    -   b) a second liquid outlet that is i) present in the lower part        of the microcavity, ii) connected to the inlet end of a second        outlet microconduit that is in downstream liquid communication        with downstream parts of the microchannel structure, and iii)        associated with a second valve that is present at the second        liquid outlet and/or in the second microconduit.

In this design the lower part of the microcavity corresponds to avolume-metering microcavity, the first liquid outlet corresponds toliquid outlet II (32) in the drawings and the second liquid outlet isnot shown in the variant of the drawing. Valves, such as the first andsecond valves are typically non-closing valves, such as capillary valveswith the preference for designs as contemplated elsewhere in thisspecification.

Constrictions and taperings are as outlined for the correspondingpositions in the upstream microcavity. See above and also unit E.

The microchannel structure in the innovative device may comprise atleast two units of A serially linked to each other such that thedownstream microcavity of an upstream unit is in liquid communicationwith the upstream microcavity of the closest downstream unit. Theserially linked units may be different in the sense that identicaloperations are not to be carried out in the upstream or downstreammicrocavity of an upstream unit as in corresponding microcavities in adownstream unit. The downstream microcavity of an upstream unit maycoincide with the upstream microcavity of the closest downstream unit.If the upstream and downstream microcavities of two consecutive units donot coincide other functional units may have been inserted between them.

An upstream microcavity (4) may comprise a) a mixing and/or dilutingfunction in which case there typically are two or more liquid inlets onthe microcavity, b) a function for separating a less dense material froma denser material as discussed for unit E below, c) a function forcarrying out one or more biochemical reactions typically selectedamongst reactions involving cells or parts of cells, enzyme reactions,affinity reactions etc, and other chemical reactions (including alsobiochemical reactions), etc. The function of the upstream microcavity(4) may be selected amongst the same general functions as for thedownstream microcavity (20) (see above) and vice versa for thedownstream microcavity (20). The functions of the two microcavities willtypically differ with respect to what is actually carried out in each ofthem. The upstream microcavity (4) may be equipped with one, two, threeor more inlets that are part of inlet arrangements as described abovefor the downstream microcavity (20).

In the case a microcavity is designed for carrying out reactions of thetypes given these reactions are typically between dissolved reactantsand/or between one or more dissolved reactants and a reactant/reactantsfirmly associated with a solid phase retained in the microcavityconcerned. If an upstream microcavity comprises a separation orfractionation function as described above and for unit E, the reactionmicrocavity is typically a downstream microcavity. In this context theterm “dissolved reactant” includes a suspended reactant, e.g. a cell ora part of a cell, a reactant immobilised to a particulate solid phasethat is in suspended form in the microcavity etc. The term “retained”means that the solid phase is maintained in the microcavity during thereaction and also after liquid that may be present during the reactionhas been at least partially removed. Typically such solid phases areinner walls, porous beds, for instance porous monoliths and packed bedsof particles preferably placed in the downstream end of the microcavityand/or in an outlet microconduit, e.g. microconduit I, or II or II′. Inthe case a porous bed is associated with an outlet, there is typicallyno separate valve function associated with the outlet. The possibilityfor performing reactions in a microcavity is typically combined withperforming mixing and/or diluting in a pre-step in the same microcavityor in an upstream microcavity (if present).

One inventive aspect related to unit A is a method utilizing amicrofluidic device in which there is a microchannel structurecomprising the innovative unit A. This method comprises the steps of:

-   -   i) providing a microfluidic device (1) in which there is a        microchannel structure (2) comprising unit A as defined above,        the upstream microcavity of said unit being filled with liquid        up to upper liquid level I, i.e. with a rear meniscus at the        upper liquid level and a front meniscus at valve I (24) in        microconduit I (17);    -   ii) moving the front meniscus by spinning the device (1) about        the spin axis (3) at a spin speed such that the front meniscus        passes valve I (24); and    -   iii) emptying the microcavity (4) down to liquid outlet I (5) by        adjusting the spin speed such that a liquid plug continuously        extends within microconduit I (17) from valve I (24) with the        front meniscus moving downstream to the outlet end (18) of        microconduit I (17) thereby discharging liquid from the upstream        microcavity (4) through the outlet end of microconduit I (17) so        that the rear meniscus passes into and if possibly through        microconduit I (17).        If the microcavity (4) has a lower part (4 b), a new meniscus        will be created inside the microcavity at the level of liquid        outlet (6). In the case microconduit I comprises an upper        extreme (22) that is above upper liquid level I and valve I (24)        is positioned upstream the upper extreme (i.e. below upper        liquid level I) the sequence “(ii) and (iii)” comprises the        steps:    -   (ii.a) moving the front meniscus over valve I (24) by spinning        the device such that the front meniscus passes the valve,    -   (ii.b) equilibrating the liquid with or without spinning such        that the front and rear meniscuses will be at equal level;    -   (ii.c) adjusting the spin speed, possibly by halting spinning if        necessary, such that capillary force will be larger than        centrifugal force at the front meniscus thereby permitting        capillary liquid transport over the upper extreme (22) until the        front meniscus is below the level of the rear meniscus; and    -   (iii′) emptying the upstream microcavity (4) down to the level        of liquid outlet I (6) via the outlet end (18) of microconduit I        (17).        During step (ii.b) the spin speed can be heavily increased, in        principle only limited by the material properties of the        microfluidic device. Accordingly very efficient        centrifugal-based fractionation of denser material from lighter        materials to upper and lower phases can be accomplished within        the upstream microcavity. Steps (iii) and (iii′) may        alternatively also comprise liquid transport without imperative        requirement for the formation of a continuous liquid plug from        valve I.

When the driving plug height (between the front and rear meniscuses) isgrowing the spin speed/centrifugal force can be successive lowered orlowered in one or more steps. This will lower the risk for undesiredand/or uncontrolled transport of liquid through liquid outlet II (32) ofthe downstream microcavity (20). This risk is caused by the increase inliquid height/hydrostatic pressure caused by the liquid transported tothe downstream microcavity (20). In the ideal case spin speed and thedesign of unit A should be adapted to each other such that the liquidheight in the downstream microcavity during at least a part of the lasthalf part of the transport is less than the sum of the driving liquidheights in the upstream microcavity (4) and microconduit I (18), forinstance with a factor F≦1, such as ≦0.75 or ≦0.5 or ≦0.25 or ≦0.1. Inthe ideal case it may be favourable if this condition is full-filledduring the whole time for the transport. This way of performing steps(iii) and/or (iii′) may be supported if

-   -   a) the height of the upstream microcavity (4) is larger than the        height of the downstream microcavity (20), for instance larger        with a factor F′≧1, such as ≧1.5 or ≧3 or ≧5 or ≧10, and/or    -   b) the largest cross-sectional area of the downstream        microcavity (20), for instance below 60% of its height, is        larger than the largest cross-sectional area of the upstream        microcavity (4), and/or    -   c) the volume of the downstream microcavity is larger (20) than        the volume of the upstream microcavity (4), e.g. with a factor        F″≧1, such as ≧1.5 or ≧2≧5.        The height of the upstream microcavity (4) is then considered to        be between the level of the top (7) and the level of the lowest        liquid outlet comprising a capillary valve, e.g. liquid outlet I        (6). The height of the downstream microcavity (20) is then        considered to be between the level of liquid inlet II (21) and        the lowest liquid outlet comprising a capillary valve, e.g.        liquid outlet II (32). This does not exclude that the height of        the upstream microcavity may be less than the height of the        downstream microcavity, e.g. F′ is <1, such as ≦0.75 or ≦0.50 or        ≦0.25. This part of the inventive aspects of unit A is also        supported if there is an upper extreme in microconduit I as        discussed elsewhere above and in the context of units B, C and        E.

The actual spin speeds (spin program) required for the different stepsdepend in a complex manner on a large number of factors and is typicallydetermined before an actual process protocol is to be carried out. Forsteps (iii) (and iii′) it is often advantageous to successively reducethe spin speed, for instance by starting the step with a relatively highspin speed and then reducing the spin speed with a factor ≧0.10, such as≧0.20 or more in one step, followed by a smoother reduction in severalsteps or continuously. Successive reduction of spin speed is particularadvantageous in the case the unit comprises a downstream microcavity(20) to which capillary valves as described above are/is associated.

The upstream microcavity (4) or an upper part (4 b) thereof may be avolume-metering microcavity of a volume-defining unit having an overflowmicroconduit (11) linked to the upstream microcavity at the level ofliquid inlet I (5). In this case step (i) typically comprises

-   -   a) providing an excess of liquid in the upstream microcavity (4)        such that the microcavity (4 a-4 b) is filled and the excess is        placed in the overflow microconduit (11) down to an overflow        valve (15 b) therein and in the inlet microconduit (8 a), and    -   b) spinning the device about the spin axis at a spin speed that        forces the liquid in the overflow microconduit (11) and in the        inlet microconduit (8 a) out through the overflow valve (15 b)        while the liquid in the upstream microcavity remains therein.        This spin speed is lower than the spin speed required for        driving liquid out through valve I (24) (and valve I′ (25), if        present), since the valve (15 b) in the overflow microconduit        (11) is designed to be weaker than other liquid outlet valves        (24 and 25 (if present)) associated with the upstream        microcavity (4). See for instance WO 02075312, WO 02075775, WO        04083108 (all of Gyros AB) etc. This will also mean that the        rear meniscus in after step (ii.b) may be below the liquid        inlet/overflow opening (5,10) of the upstream microcavity (4).

Variants of unit A in which liquid outlet I (5) divides the upstreammicrocavity (4) into an upper part (4 a) and a lower part (4 b) asdiscussed above can be used for separation of a liquid that containsdenser material and less dense material (lighter material) into an upperphase that contains the lighter material and is placed and a lower phasethat contains the denser material by spinning the device containing theunit about a spin axis. The actual separation into the two phases ismost efficiently carried out by spinning during in step (ii.b) above,i.e. microconduit I (17) comprises an upper extreme (22) that is above(not shown) the upper liquid level I in the upstream microcavity (4)with valve I (24) placed upstream of the extreme and below upper liquidlevel I. In other variants of unit A, the actual separation into the twophases is taking place between steps (i) and (ii) by spinning the deviceat a spin speed that is below the spin speed required for liquid to passthrough valve I (24) but typically higher than the spin speeds used instep (i) and many times also higher than the spin speed used in step(iii). In this latter variant of the method, microconduit I (17)preferably has an upper extreme (22) that is below upper liquid level Iwith valve I (24) placed upstream of the extreme (22) and at a levelthat is below upper liquid level I. The centrifugal separationsdescribed in this paragraph may be applied to (1) reaction mixturesobtained by reacting dissolved reactants with a reactant immobilised toa suspended solid phase in particulate form, (2) samples containingcells or parts of cells, such as cell culture supernatants, cellhomogenates, tissue homogenates, whole blood, etc, See also thedescription and use of unit E.

B. Functional unit comprising a capillary valve in an upwardly directedmicroconduit This unit comprises a liquid transport microconduit I (17)with an inlet end (16) and an outlet end (18) and between the ends acapillary valve I.

The characterizing feature is that microconduit I (17) comprises anupwardly directed section (23 a) that extends over a part of or over thefull length of microconduit I (17). In the preferred variants capillaryvalve I (24) is present in an upward section (23 a).

This innovative microconduit is part of a microchannel structure (2) ina microfluidic device (1). The device, the microchannel structure andthe unit are typically designed to permit spinning about a spin axis (3)to create a force, for instance centrifugal force and/or hydrostaticpressure, that will drive a liquid aliquot abutting the upstream side ofvalve I (24) to pass through the valve for further transport andprocessing in parts of the structure that are downstream of valve I(24). Capillary force in the form of self-suction may be used as asupplement for the transport, for instance during non- or low-spinningconditions and in particular in order to transport a liquid aliquot orits front meniscus from a lower level to an upper level and/or from aliquid inlet port to a first valve position of a microchannel structure(port=opening in the surface of the device). The unit may also bepresent in a microfluidic device in which forces other than the onesmentioned are utilized in the transport of liquid through valve I and/orin or between different parts of the microchannel structure. Typicalsuch other forces are gravitational force of earth, etc.

Inlet end (16) of microconduit I (17) is typically at a higher levelthan the outlet end (18) which does not exclude that in some variants itmay be the other way round with outlet end at the higher level and theinlet end at the lower level.

Microconduit I (17) may be directed continuously upwards or may containtwo or more sections that alternating are directed continuously upwardsor continuously downwards. The inlet end (16) and/or the outlet end (18)may be part of an upward section, a downward section or a horizontalsection. The term “horizontal” means that the section all along is at aconstant level which for centrifugal based systems means at anessentially constant radial distance (arc-shaped) including a straightline that has a tangential/orthogonal direction relative to a radiusgoing through centre of the section. The angular length of a horizontalsection, if any, is ≦π/20 radians or ≦π/40 radians or ≦π/80 radians.“Continuously upward” and “continuously downward” includes that asection may contain a stretch (=part of a section) that is “horizontal”.Horizontal sections may be present between an upward and a downwardsection. An upward and a downward section (23 a,23 b) that are next toeach other possibly with a horizontal section between them typicallyform an upward or a downward turn (“elbow”) with an upper extreme (22)or a lower extreme, respectively. In preferred variants microconduit I(24) is shaped as an upward turn with its inlet end (16) at a level thatis above or below the level of its outlet end (18), possibly with ahorizontal section at one or both of its ends.

Capillary valve I and other capillary valves in unit B may be of thesame type as in unit A. See unit A and General about MicrofluidicDevices, Background Technology and publications cited in these parts ofthe specification. In preferred embodiments capillary valve I may be afinger valve as defined for unit C.

Capillary valve I (24) is preferably placed in an upward or a horizontalstretch, if present, of an upward section (23 a) and/or at a level thatis equal to or above the level of inlet end (16). This upward section(23 a) may be part of an upward turn with an upper extreme and theoutlet end (18) of microconduit I (17) at a lower level than the inletend (16). In the case microconduit I (17) contains a downward section,for instance with outlet I (18) at a lower level than inlet end (16),capillary valve I (24) may be placed in the downward section at a levelabove or below the level of inlet end (16).

Microconduit I (17) may also comprise one or more additional capillaryvalves, for instance a valve (25) at the inlet end (16) of microconduitI (17) provided that capillary valve I (24) is positioned withinmicroconduit (17). See further unit D but also units A and C.

The inlet end (16) of microconduit I (17) may be connected to anupstream microcavity I (4) that may be

-   -   a) separation microcavity e.g. of the type described for units A        and E,    -   b) a volume-metering microcavity (4 a), e.g. of the type        discussed for unit A and in WO 02074438 (Gyros AB) with a valve        corresponding to valve I associated with the liquid outlet that        is used for controlling downstream transport of a metered        aliquot,    -   c) a liquid retaining microcavity, such as a mixing and/or        reaction microcavity e.g. of the types suggested in WO        2003018198 (Gyros AB), WO 2005094976 (Gyros AB),        PCT/SE2005/001887 and U.S. Ser. No. 11/___, ___ filed in the        name of Gyros Patent AB Dec. 12, 2005 “Microfluidic Assays and        Microfluidic Devices”), etc with one, two or more inlet        functions with or without a valve between an inlet function and        the microcavity and a valve (corresponding to valve I) at its        liquid outlet,    -   d) a reaction microcavity of the type described in WO 02075312,        i.e. having one or more liquid inlet, each of which may or may        not be associated with a valve, and a liquid outlet that is        associated with a flow restriction that control liquid flow        through the microcavity and/or a valve in a liquid inlet,    -   e) etc.        Retaining microcavities in general are described in WO 03018198        (Gyros AB), for instance. Flow restriction means includes a        narrow and relatively long outlet microconduit, a porous bed and        membranes in the reaction microcavity etc. See WO 02075312        (Gyros AB) and WO 03024598 (Gyros AB). Capillary valves are        preferred with finger valves, for instance of the innovative        kind described in this specification, being preferred at outlet        functions of reaction microcavities, separation microcavities        and mixing microcavities.

The inlet end (16) of microconduit I (17) may alternatively be a) a partof a microconduit branching that comprises two or more inlet and/oroutlet ends of other microconduits that are intended for liquidtransport, or b) directly or indirectly connected to a liquid inlet portof the microchannel structure (i.e. an opening in the surface of thedevice containing the microchannel structure containing the unit).

The outlet end (18) of microconduit I (17) may be directly connected toa downstream microcavity II (20) that may be a reaction microcavity, aseparation microcavity, a volume-defining unit/volume-meteringmicrocavity etc as discussed for units A and E and for the upstreammicrocavity (4) in the preceding paragraph with the proviso thatmicroconduit I (17) is part of a liquid inlet function of microcavity II(20).

The outlet end (18) of microconduit I (17) may alternatively be a) partof a microconduit branching that comprises two or more inlet and/oroutlet ends of other microconduits that are intended for liquidtransport, or b) directly or indirectly connected to a liquid outletport of the microchannel structure (i.e. an opening in the surface ofthe device containing the microchannel structure containing the unit).

One inventive aspect related to unit B is a method for transportingliquid in a microchannel structure that comprises this unit and ispresent in a microfluidic device. This method comprises the steps of:

-   -   i) providing a microfluidic device in which there is a        microchannel structure (2) that comprises unit B, typically with        an upstream microcavity (4) connected to the inlet end (16) of        microconduit I (17), and with none, one, two or more capillary        valves upstream of capillary valve I (24) in microconduit I (17)        and with a front meniscus of an aliquot of a liquid at the first        capillary valve in microconduit I (17) and a rear meniscus        placed upstream of the inlet end (16) typically at a level above        the level of valve I (24),    -   ii) moving the front meniscus successively across the capillary        valves of microconduit I (17) that are upstream of capillary        valve I (24) by applying a driving force on the liquid aliquot        and halting the front meniscus at capillary valve I (24), with        the proviso that this step is only carried out if there are one        or more capillary valve(s) upstream of capillary valve I (24) in        microconduit I (17),    -   iii) moving the front meniscus across capillary valve I (24)        -   a) subsequent to step (i) if no capillary valve is present            upstream capillary valve I (24) (i.e. capillary valve I is            the first capillary valve in microconduit I), or        -   b) subsequent to step (ii) if said one or more capillary            valves are present in microconduit I,    -    by applying sufficient driving force on the aliquot when the        front meniscus is to be forced across a capillary valve,    -   iv) moving at least a part of the aliquot to a part of        microconduit I (17) that is downstream of capillary valve I (24)        and typically also downstream of the outlet end (18) of        microconduit I (17) by applying a sufficient driving force on        the aliquot to bring it at least across capillary valve I.        The rear meniscus in step (i) is typically a meniscus of the        same aliquot as the front meniscus. The rear meniscus is        typically present in the upstream microcavity (4) (if present).        In the most common variants there are no capillary valves        upstream of capillary valve I (24) in microconduit I (17). If        such a capillary valve(s) is/are present then one of them is        preferably located to the inlet end (16) of microconduit I (17).

Preferred variants also encompass that the microfluidic device (1)provided in step (i) is capable of being spun about a spin axis (3) suchthat centrifugal force possibly combined with hydrostatic pressurecreated within the structure during spinning is capable of creating adriving force that pushes the front meniscus across the capillaryvalve(s) in microconduit I (17) (step (ii) and/or step (iii)) and thedownstream transportation between the valves (in step (ii)) and aftercapillary valve I (24) (step iv). The combination with hydrostaticpressure are important for valve(s) that is/are placed within an upwardsection (23 a) for instance encompassing the inlet end (16) ofmicroconduit I (17). Capillary force may be used as an alternativeand/or as a supplement to centrifugal force to reach the next subsequentcapillary valve after one valve has been passed, or for downstreamtransportation once the last capillary valve in microconduit I (17) hasbeen passed, for instance capillary valve I (24), such as in step (iv).The latter downstream transportation in particular applies if the upwardsection (23 a) is part of an upward turn that has an upper extreme (22)that is above the initial rear meniscus or upper liquid level I in theupstream microcavity (4) such as above the uppermost part (7) of theupstream microcavity (4). See unit A.

In certain variants of the method aspect, microconduit I (17) has anupward turn and valve I (24) in the upward section (23 a) of the turn.It is then advantageous to form a continuous liquid plug from valve I(24) with the front meniscus in the downward section, such as below thelevel of the rear meniscus in the upstream microcavity (4) and/or belowupper liquid level I of the uppermost part (22) of the turn and/or belowthe level of the inlet end (16) of the microconduit I (=liquid outlet(6) of the upstream microconduit (4)). This liquid plug will assist inthe transportation such that the spin speed can be reduced once thefront meniscus has passed the highest level/upper extreme (22) ofmicroconduit I (17). For details see unit A.

Unit C. Capillary Stop Function (Finger Valve, Finger Vent Etc)

This unit comprises a microconduit I (17) with an inlet end (16) and anoutlet end (18) and a capillary stop function. Depending on design andposition within a microchannel structure, microconduit I (17) can beused as a liquid transport microconduit or a vent microconduit

A segment (46) of microconduit I (17) defines a capillary stop function(24) by containing a sharp change in geometric surface characteristicssuch as a sharp change in a cross-sectional dimension (lateral change,not shown), and/or a sharp increase in non-wettability in chemicalsurface characteristics. The change and/or increase are typically local(44 a or 44 b) within the microchannel structure in the sense that thesegment (46) may have a certain length encompassing the whole ofmicroconduit I or a part thereof. The segment thus encompasses none, oreither one or both of the ends of microconduit I. For increases innon-wettability characteristics this means that at least one, two ormore of the inner walls of the microconduit comprises this kind ofchange as described in Background Technology, General about MicrofluidicDevices and publications referenced in these parts of the specification.

Inlet end (16) of microconduit I (17) is typically at a higher levelthan outlet end (18) which does not exclude that in some variants it maybe the other way round with outlet end (18) at the higher level andinlet end (16) at the lower level.

The capillary stop function of this unit has two different primary uses:a) a vent solely for inlet or outlet of gas/air, and b) a stop/flowvalve for liquid transported through the microconduit. Use (a)contemplates that the inlet end (16) of microconduit I is intended to bein contact with liquid while the outlet end (18) shall only be incontact with air/gas. Use (b) contemplates that both ends are to be incontact with liquid, successively and/or concomitantly.

The characterizing feature is that at least a part of the segment isdivided into two or more microchannels (fingers) (42) and the inventivecapillary stop function (24) is therefore a finger valve or a fingervent. The inner surface area defined by the change in surfacecharacteristics is present within the microchannels (42) or abutted toor covering the inlets (45) and/or the outlets (43) of the microchannels(42). Sharp changes in geometric surface characteristics include e.g.sharp increases in a lateral cross-sectional dimension defined by theinlet ends (45) or the outlet ends (43) of the microchannels (42). Aninner surface area of increased non-wettability (44 a) may start and/orend at the inlet ends (45) and/or the outlet ends (43) of themicrochannels (42) and/or may be completely within the microchannelsand/or cover either one (44 b) or both of the inlet ends (45) and theoutlet ends (43) of the microchannels (42). The area of increasednon-wettability may be divided into two or more subareas associated withthe same stop function, for instance one subarea at the inlet ends ofthe microchannels and another one at the outlet ends of the samemicrochannels. The inner surfaces of the microchannels between two suchsubareas are typically wettable. Abutment or coverage of only the inlets(45) or only the outlets leaving the opposite ends hydrophilic oftengives advantages (see below).

The segment (46) defined above in the innovative capillary stop function(24) extends between

-   -   a) the most upstream of the upstream ends (45) of the        microchannels (42) and the upstream end (47) of the non-wettable        surface area (44 a or 44 b), and    -   b) the most downstream of the downstream ends (43) of the        microchannels (42) and the downstream end (48) of the        non-wettable surface area (44 a or 44 b).

The number of microchannels (42) is typically two, three, four, five,six or more with an upper limit typically being fifteen, twenty, thirty,fifty or more. At least two of the microchannels in a capillary stopfunction of the invention are functionally equal in the sense that a) noliquid passes through any of the microchannels when the function is apure vent, and b) liquid can pass through at least two, such as all, ofthe microchannels in parallel when the function is a stop/flow valve (infact essentially in parallel since a time variation for break throughbetween the microchannels from 0 up to 15 seconds at use may beacceptable). This includes that the individual microchannels (42) inessence should have the same shape with respect to one or more features,selected amongst length, curvature, and cross-sectional dimensions likedepth, width, area etc, longitudinal variations etc. The microchannels(42) of a capillary stop function of the finger type are thus distinctand well-defined in the sense that they are not random pores with aspectrum of directions and intersections as in conventional porousplugs, beds, membranes and filters.

The area of changed surface characteristics may partially or completelycover microconduit I (17), e.g. start at, before or after the inlet end(16), and/or end at, before or after the outlet end (18) of microconduitI.

The length, depth and width of a microchannel (42) depend among otherson the stop function being a valve or a vent, the size and form ofcross-sectional dimensions of the microconduit before and/or aftermicrochannels, cross-sectional dimensions of the individualmicrochannels, desired flow rate before or after the microchannels,desired driving force including spin speed for centrifugal baseddevices, position on the device, fabrication technique etc.

The lengths of individual microchannels (42) may be different or equalfor two or more, such as all, of them. Typical lengths of a microchannelare ≧0.1, such as ≧0.5 or ≧0.75 or ≧1 or ≧3 or ≧5 or ≧10, and/or ≦10² or≦10³ or ≦10⁴ or ≦10⁵, times the largest of its width and depth of themicrochannel. In the case the width and depth varies along the length ofa microchannel then the comparison is with the largest width and largestdepth. In absolute figures typical lengths are found in the intervals ≧5μm, such as ≧10 μm≧50 μm≧100 μm or ≧500 μm or ≧1 000 μm or ≧3 000 μm,and/or ≦50 000 μm, such as ≦25 000 μm or ≦10 000 μm or ≦5 000 μm or ≦1000 μm.

The depth and/or width are typically different or equal for two or more,such as all, of the microchannels (42). In absolute figures typicaldepths and/or widths are ≧1 μm, such as ≧5 μm≧10 μm or ≧20 μm≧50 μm,and/or ≦500 μm, such as ≦200 μm or ≦100 μm or ≦50 μm or ≦20 μm.

In the case the microchannels (42) are shorter than microconduit I, thesum of the open cross-sectional areas (A_(sum)) of the microchannels(42) at their upstream end (45) and/or their downstream end (43) isequal to or larger or smaller than the open cross-sectional area of themicroconduit (42) immediately before and/or after the segment(A_(before), A_(after)). The ratio A_(sum)/A_(before) (and/orA_(sum)/A_(after)) is typically in the interval ≧1, such as ≧2 or ≧5 or≧10, and/or ≦1, such as ≦0.5 or ≦0.2 or ≦0.1. In the case of differentdepths and/or widths at a certain position the intervals refer to thelargest depths and largest width at the position. Compare withtrapezoidal or triangular cross-section.

In valve variants of unit C, the inlet end (16) and/or the outlet end(18) of microconduit I (17) is typically part of a branching orconnected to a microcavity as described for units A, B and E. The inletend (16) of may alternatively be directly or indirectly connected to aninlet port and the outlet end of the same microconduit similarly to anoutlet port. In principle any combination of functionalities as referredto in different parts of this specification may be associated withmicroconduit I in a form comprising the inventive finger valve after theappropriate adaptation.

In vent variants of unit C (not shown), the inlet end of microconduit Iis typically directly linked to a microcavity intended to contain liquidor a microconduit to be used for the transport of liquid. The outlet endof microconduit I is then in direct or indirect communication withambient air, possibly via one or more air/gas microconduits, and/or withother parts of the same microchannel structure or with parts of othermicrochannel structures on the same microfluidic device. This otherparts are also contemplated as microcavities/microconduits for air/gas.The innovative finger vent function is preferably located to the inletend of microconduit I, or alternatively microconduit I comprises anadditional capillary stop function that is placed at this position. Thisadditional capillary stop function may or may not be a finger vent.

Microconduit I (17) may downstream or upstream of a finger function (24)contain a section that have a larger or smaller cross-sectional areathan on the other side of the function, preferably with a smallercross-sectional area downstream of the function than upstream thereof.This in particular applies if the finger function is a finger valve.Compare unit A.

Microconduit I (17) may contain one or more additional capillary valves.One (25) of these extra valves is preferably placed upstream of thefinger valve (24) and then preferably located at the inlet end (16) asdescribed for the other innovative units of this specification (inparticular unit D). One or more of these additional capillary valve(s)may be a finger valve or a capillary valve of the kinds described inBackground Technology, General about Microfluidic Devices andpublications referenced in these parts of the specification.

An interesting finger valve may be accomplished if the innovative fingervalve

-   -   a) is placed at the outlet end (16) of microconduit I (17),        typically extending from the inlet end (16) to the outlet end        (18) of microconduit I (segment (46)=microconduit (17)), or    -   b) its non-wettable area (43 a) is abutted to or is covering the        upstream ends (47) of the microchannels (42) but not the        downstream ends (48) of the same microchannels, and the        downstream ends of the microchannels are in fluid communication        with means that permits selective wetting of the interior of the        microchannels from this end of microconduit I/the microchannels.

A particular preferred variant of (a) comprises that valve I (=thesegment) and microconduit I coincide and that the inlet end of valveI/microconduit I is directly attached to an upstream microcavity and theoutlet end of valve I/microconduit I is directly attached to adownstream microcavity. Both these microcavities can be selected asoutlined for the upstream microcavity (4) and the downstream microcavity(20) of unit A. See above.

For variant (b) above the term “means for selective wetting” includes a)a downstream microcavity that has a wetting inlet in fluid communicationwith the outlet end of microconduit I, and b) that the outlet end ofmicroconduit I is part of a branching that comprises the end of amicroconduit in which liquid can be provided separately to thedownstream end of the microchannels. When liquid is provided via thiskind of wetting means, liquid will be sucked into the hydrophilicmicrochannels up to the non-wettable part. One can envisage that thiskind of valves will require an increased liquid pressure forbreakthrough in the downstream direction and therefore make themsuitable for use in outlet ends of reaction microcavites, mixingchambers and other retaining microcavities in which liquid is to beretained under pressure. For various kinds of microcavities see Generalabout Microfluidic Devices.

Microconduit I (17) of unit C may have one or more upward sections (23a) as described for unit B, preferably with the finger valve (24) in atleast one of these sections. The upward section (23 a) may be part of anupward turn as described elsewhere in this specification. Microconduit Imay also have other shapes as discussed for units A-B.

One inventive aspect related to unit C is a method utilizing amicrofluidic device in which there is a microchannel structurecomprising this unit. This method is a method for transporting a liquidacross the capillary stop function of unit C. The method comprises thesteps of:

-   -   i) providing a microfluidic device in which there is a        microchannel structure that comprises unit C as defined above        with a front meniscus of an aliquot of a liquid at a position        upstream of the capillary stop function (24) and a rear meniscus        placed upstream of the inlet end (16) typically at a level above        the level of the capillary stop function (24), and    -   ii) moving the front meniscus        -   a) to and across the capillary stop function if the function            is a valve, possibly by first halting and then resuming            movement the front meniscus at the stop function, or        -   b) to the function if the function is a vent    -    by applying a driving force        The rear meniscus in step (i) is typically a meniscus of the        same aliquot as the front meniscus. The rear meniscus is        typically present in the upstream microcavity (4) (if present).

The driving force in steps (i) and (ii) may be air/gas overpressure orhydrostatic pressure applied to a rear meniscus of the aliquot,centrifugal force etc. The transport/moving to the capillary stopfunction (24) may also utilize capillary force. Passing across thecapillary stop function (24) typically require an active increase indriving force which means that the driving force can be selected amongstthe same forces as for the initial moving with exclusion of capillaryforce that is not suitable. If the device is designed for utilizingcentrifugal force, an increased spinning is preferred. After step (ii)other driving forces or combination of forces than in step (ii) mayalternatively be used for bringing the aliquot or a part of it furtherdownstream into the microchannel structure. Centrifugal force may forinstance be replaced with and/or supplemented with capillary forceand/or hydrostatic pressure. In the case the finger valve is linked toor is part of any other of the units A-F, steps (i) and (ii) areaccordingly adapted to the requirement of the steps of the correspondingmethod.

Unit D. Protected Capillary Valve Unit.

This unit comprises a liquid transport microconduit I (17) with an inletend (16) and an outlet end (18) and comprising a capillary valve I (24).

The characterizing feature is that the microconduit comprises one ormore additional capillary valves (25). Capillary valve I (24) ispreferably a finger valve, typically as defined for unit C, with one ormore of the additional valves placed upstream of valve I. An additionalcapillary valve may also be a finger valve or of the kinds discussedelsewhere in this specification for other units, in BackgroundTechnology, in General about Microfluidic Devices and in publicationsreferenced in these parts. One of the additional valves (25) ispreferably placed at the inlet end (16) of microconduit I (17) with theproviso that valve I (24) then is placed within the microconduit.

This innovative microconduit I (17) is part of a microchannel structurein a microfluidic device of the same kind as discussed for unit A-C andE-F.

Inlet end (16) of microconduit I (17) is typically at a higher levelthan the outlet end (18) which does not exclude that in some variants itmay be the other way round with outlet end (18) at the higher level andinlet end (16) at the lower level.

As described for units B and C, microconduit I (17) may contain one ormore upward sections (23 a) and/or one or more downward sections (23 b)and/or one or more horizontal sections, one or more upward turns, one ormore downward turns, upper extreme(s) (22) etc. Capillary valve I, suchas in the form of a finger valve, may be present in any of these parts,most typically in an upward or a downward section of an upward turn withdue care taken for the desired function in each particular case. Fordetails see units B and C.

The inlet end (16) or the outlet end (18) of microconduit I (17) in unitD is typically part of a branching or connected to a microcavity asdescribed for units A, B, C and E. The inlet end (16) of microconduit Imay alternatively be directly or indirectly connected to an inlet portand the outlet end (18) to an outlet port. In principle any combinationof the functionalities referred to may be associated with microconduit Iof unit D provided the proper adaptation is made.

One inventive aspect of unit D is related to a method for transporting aliquid in a microchannel structure comprising unit D. This method isapplicable also to units B and C if they comprise two or more capillaryvalves as described above The method comprises the steps of:

-   -   i) providing a microfluidic containing a microchannel structure        containing unit D;    -   ii) providing a liquid aliquot abutted to the most upstream of        the capillary valves (=valve 1, front meniscus at valve 1);    -   iii) moving the aliquot or a part thereof (front meniscus)        across valve 1 by increasing the driving force and halting the        meniscus at the next capillary valve (valve 2), possibly with a        decrease in driving force after the meniscus has passed valve 1;    -   iv) moving the meniscus across valve 2 by increasing the driving        force and halting the meniscus at the next capillary valve        (valve 3) (if any), possibly with a decrease in driving force        after the meniscus has passed valve 2,    -   v) repeating steps (iii) and (iv) until all the capillary valves        of microconduit I have been passed,    -   vi) moving the meniscus through the outlet end of microconduit        I.        This method also comprises that the rear meniscus is placed as        described for the method aspects of unit B and C.

Due to the hydrophilicity of the microconduit (self-section) the drivingforce can be decreased after passage of each individual capillary valve,i.e. one can rely partly or wholly on capillary transport (passive)between the valves.

In preferred variants the device is adapted for using centrifugal forceobtained by spinning the device. Increasing the driving force then meansincreased spinning. For variants in which unit D is incorporated intoany of the other units described in this specification the method abovemay be adapted to the method given for these units.

As discussed in the context of other units of this specification,microconduit I (17) typically comprises at most two capillary valves(25,24) with the most upstream one (25) being a capillary non-fingervalve preferably placed at the inlet end (16) and the subsequent valve(24) preferably being a capillary finger valve.

In preferred variants the inlet end (16) of microconduit I (17) definesan intersection between microconduit I and a transport pathway in whichliquid containing material that may lower the efficiency of a capillaryvalve, which is downstream of the first capillary valve is transported,by-passes the inlet end of microconduit for downstream parts of thepathway. These downstream parts are typically not coinciding withdownstream parts of the pathway branching into microconduit I. Seediscussion of variants of units A-E in which the upstream microcavity(4) that may be present may have a lower part (4 b) corresponding to adownstream part of a transport pathway for material that can be harmfulfor capillary valves, for instance by clogging or by adsorption. Typicalharmful materials are discussed in the context of problems overcome bythe invention and in the context of particular units.

Unit E. Unit for Separating an Upper Phase Typically a Liquid Phase froma Denser Phase Typically Containing Particulate Material.

The unit comprises:

-   -   d) an separation microcavity (4) with a liquid inlet I (5) and a        liquid outlet I (6) with the former being at a higher level than        the latter,    -   e) a liquid transport microconduit I (17) that has an inlet end        (16) directly connected to liquid outlet I (6) and an outlet end        (18) that is at a lower level than the inlet end (16) (and        liquid outlet I).

The separation microcavity corresponds to the upstream microcavity inunit A. Liquid outlet I (6) is placed at an intermediary level betweenthe level of the lowest part (8) and the level of the top part (7)(uppermost part) of the separation microcavity (4) and defines a lowerpart (4 b) and an upper part (4 a) of the microcavity (4).

The separation microcavity (4) is capable of retaining a predeterminedliquid volume which defines an upper liquid level I in the microcavity.This upper liquid level is equal to or lower than the level of theuppermost part (7) the microcavity, and above the level of liquid outletI (6).

The microfluidic device that contains the microchannel structure inwhich the unit is a part is designed to permit spinning about a spinaxis in order to manage a separation of a liquid containing a denser anda lighter material into an upper and a lower phase, and to export theupper phase to downstream parts of the microchannel structure via liquidoutlet I (6) and microconduit I (17). The export to downstream partsutilises centrifugal force created by the spinning, and/or hydrostaticpressure built up within the microchannel structure during spinning,and/or capillary force. Other forces may also be used, e.gelectrokinetic forces, in combination with one or more the forces justmentioned. See also “General about Microfluidic Devices”.

The characterizing feature comprises that:

-   -   a) microconduit I (17) is associated with a valve I (24),        preferably a capillary valve I, and    -   b) the flow direction through liquid outlet I (6) is directed        upwards, and/or    -   c) liquid outlet I (6) is placed in an downwardly turned part of        an inner wall of the separation microcavity (4), and/or    -   d) the microconduit part next to the inlet end (16) of        microconduit I (17) is directed upwards.        Valve I (24) may be placed within or at the inlet or outlet end        (16 or 18) of microconduit I and is in most variants so far        envisaged preferably a finger valve of the type described for        unit C. The cross-sectional dimension of microconduit I should        in many variants be larger upstream than downstream of valve I,        with a factor e.g. ≧1, such as ≧2 or ≧5 or ≧10. This in        particular applies if valve I is a finger valve and/or if        creation of a driving liquid height/plug is to be formed in the        microconduit when in use. See units A-C.

Microconduit I (17) typically has an upper extreme (22) that preferablyis placed either at the inlet end (16) (at liquid outlet I (6)) orinternally within the microconduit (upper extreme=elbow directedupwards). This upper extreme (22) may be at the same level as liquidoutlet I (6) of the separation microcavity (4) in which casemicroconduit I in preferred variants has a first short horizontalsection followed by a downward section down to the outlet end (18). Theupper extreme (22) may alternatively be above the level of liquid outletI (6), such as above upper liquid level I of the separation microcavity(4) and even above the level of the top (7) of the separationmicrocavity (4). In these latter variants the upper extreme (22) istypically within a variant of microconduit I (17) that starts with anupward section (23 a) followed by a downward section (23 b) where thejoint between the sections defines the upper extreme (22). This kind ofupper extreme may comprise a horizontal section between the upward anddownward sections. In the variants of this paragraph, valve I (24) istypically placed at or if possible upstream of the upper extreme (22)(i.e. in the upstream section (23 a)) and above or below upper liquidlevel I, such as above 25% of the height between the inlet end (16) andthe upper extreme (22). The preferred relative position of the valvewithin the upstream section (23 a) is preferably even higher, such asabove 50% or above 75% of the height between the inlet end (16) and theupper extreme (22).

In one of the most preferred variants valve I (24) is placed in anupward section (23 a), and below the level of upper liquid level I andthe upper extreme (22). Filling a predetermined volume of liquid intothe microcavity (4) will place a rear meniscus at upper liquid level Iand a front meniscus at the first valve in the microconduit (17), suchas at valve I (24) if only no additional valve as described elsewhere inthis specification is present. Subsequent spinning of the device willequilibrate the rear and front meniscuses to the same level and abovethe level of valve I (24). By slowing down the spinning capillary forcewill take the front meniscus over the upper extreme (22) whereafterresumed high spinning will quickly empty the upper part (4 a) of theseparation microcavity (4) down to the level of liquid outlet I (6). Asfor unit A the spinning speed can be reduced during emptying if acontinuous liquid plug is maintained while the front meniscus is movingdownwards. This includes that dimensions, shapes inner volumes etc ofthe separation microcavity (4) and microconduit I (17) are properlyadapted to each other. See also the description of units A-C and thecorresponding method aspects in which also other relative positions aregiven.

Valve I (24) may also be placed downstream the upper extreme.

Microconduit I (17) may also contain an extra valve (25) placed upstreamof valve I (24), in particular if valve I (24) is a capillary fingervalve or some other kind of valve that has a tendency to be clogged orotherwise harmed by the liquids used, This extra valve is preferablyplaced at the inlet end (16) of microconduit I (17) and selected to beless prone to be harmed by the liquids used. This variant may also beuseful in the case microconduit I (17) contains downward turns or othershapes that promotes collection of particulate material and liquids atpositions upstream of valve I (24).

See units A-D for alternative shapes of microconduit I and positioningof valves within microconduit I.

Capillary valves in the unit, such as valve I (24), are typically basedon a change in chemical and/or geometric inner surface characteristicsin a hydrophilic flow path of the unit according to principles that arewell-known in the field. The change may be as a sharp increase incross-sectional dimension of a microconduit (lateral change) and/or asharp increase in non-wettability of an inner surface of a microconduit,in both cases in the flow direction. The change is typical local(break), for instance a non-wettable/hydrophobic surface break in anotherwise hydrophilic flow path. The inner non-wettable surface may beroughened and/or expose fluorohydrocarbon groups. See further underBackground Technology and General about Microfluidic Devices and thepublications referenced under these headings.

The liquid flow starting to exit through liquid outlet I (6) may havevarious directions in relation to the centrifugal force at liquid outletI (6). The flow direction may thus comprise (a) an upward/inwardcomponent (inward radial component), or (b) essentially tangential(horizontal). The flow direction relative to the direction of thecentrifugal force at liquid outlet I (6) may thus be for alternative (a)at least partially against the centrifugal force, and for alternative(b) essentially orthogonal against the centrifugal force. Expressed asan angle (α) relative to the direction of centrifugal force at liquidoutlet I this may be for alternative (a) 90°≦α≦270°, such as 95°≦α≦265°(against), and for alternative (b) 90°≦α≦100°, such as 90°≦α≦95°, and/or260°≦α≦270°, such as 265°≦α≦270° (orthogonal)

The angle (α′) between the centrifugal force at liquid outlet I (6) andthe inner wall around liquid outlet I (6) may be for alternative (a)−90°≦α′≦0° and/or 0°≦α′≦90°, such as −90°≦α′≦−5 and/or 5°≦α′≦90°, andfor alternative (b) −10°≦α′≦10°, such as −5°≦α′≦5° or in particularα′=0°. The direction of the inner wall and/or of the correspondingopening in alternative (b) essentially coincides with the direction ofthe centrifugal force.

The part of microconduit I (17) that is next to liquid outlet I (6) ofthe separation microcavity (4) preferably has a direction selectedamongst the main directions for flow through this liquid outlet althoughthe two directions do not need to be the same.

Liquid outlet I (6) divides the separation microcavity (4) in a lowerpart (4 b) and an upper part (4 a) as discussed for unit A above. Intypical cases the lower part (4 b) constitutes ≧10%, such as ≧25% or≧50% or ≧70% or ≧80% of the total volume of the separation microcavity(4). The exact relative volumes of the parts are determined by therelative volumes of the phases obtained after their formation byspinning of the device. It is often important that the lower part (4 b)should have at least the same volume as the lower phase. Thus the lowersurface of the phase to be exported through liquid outlet I (6) shouldbe below the level of this outlet, e.g. by leaving a liquid heightbetween this lower surface and liquid outlet I (6) ≧10 μm≧50 μm≧100μm≧200 μm.

The separation microcavity (4) may be tapered towards the level of aninlet (5) and/or an outlet (6) or towards this inlet and outlet as such.Tapering typically means that at least one, two or more of the innerwalls at the outlet/inlet concerned form an acute angle (β<90°) with themain flow direction through the tapering or with a straight line(radius) going from the spin axis towards the outlet concerned. Thisangle (β) preferably is within the interval of 10-60°, more preferably20°-40°, such as 25°-35° with preference for about 30°. These intervalsare applicable also to pure vent outlets. With respect to liquid outletsand pure vent outlets tapering will counteract air bubble formationduring filling of the microcavity with liquid.

The separation microcavity (4) may be constricted at the level of liquidoutlet (6). This constriction may be defined by the tapering discussedin the preceding paragraph.

The constriction and/or tapering means that the largest cross-sectionalarea of the microcavity, or of an upper and/or lower part thereoftypically is larger than the cross-sectional area at the level of theoutlet/inlet concerned with a factor ≧1, such as ≧1.25 or ≧1.5 or ≧3.0or ≧5.0.

In preferred designs the cross-sectional area in the upstreammicrocavity is typically larger upstream of liquid outlet I (6) than inmicroconduit I (17), e.g. with a factor ≧1, such as ≧2 or ≧5 or ≧10.

Additional details about tapering and constrictions are given for unitA.

The lower part (4 b) of the separation microcavity (4) is typicallycommunicating with one or more outlets (14) to ambient atmosphere solelyfor venting out air displaced by liquid entering this part. The actualopening (14) (vent outlet port) in the surface of the device for anoutlet of this kind is preferably located at a higher level than liquidinlet I (5) and typically also at a higher level than the correspondingactual inlet opening (9) in the surface of the device through whichliquid is initially introduced (liquid inlet port). There may be acapillary stop function (15 a) (downstream end) associated with thiskind of outlet(s), in particular if the corresponding vent outletopening (14) in the surface of the device is at a lower level than theliquid inlet (5) of the upstream microcavity (4). It follows that theseparation microcavity (4) may form a U-shaped or downward turnmicrocavity. In the case there are several vent outlet openings (14) inthe downstream part (4 b) of the microcavity, this part (4 b) may bedivided into two or more fingers (finger microcavity).

The upper part (4 b) of the upstream microcavity (4) may be used as avolume-metering microcavity, if there for instance is an overflowopening (10) at the level of liquid inlet I (5). See below. Thismetering is likely to be more accurate if the capillary stop function(15 a) associated with a vent outlet function (14) of the type discussedis placed at a lower level than liquid outlet I (5). The capillary stopfunction (15 a) preferably is a finger vent as described for unit C. Seealso unit A for further details.

The lower part (4 b) may also have a liquid outlet I′ for export ofmaterial from the lower part after the upper part has been emptied vialiquid outlet I (not shown). In this case liquid outlet I′ is at a lowerlevel than liquid outlet I.

The upper part (4 b) of the separation microcavity (4) may be part of avolume-defining unit, for instance of the type outlined for the upstreamor downstream microcavity of unit A or in WO 02074438 and WO 03018198(both of Gyros AB). In short this typically means that liquid inlet I(5) is connected to an inlet microconduit I (8 a) in which there is anoverflow opening (10) at the same level as liquid inlet I (5). Theoverflow opening (10) is connected to a downwardly directed overflowmicroconduit (11) through which excess liquid added through the inletmicroconduit can be selectively discarded by the proper spinning of thedevice.

The upper part (4 b) may also contain one or more additional liquidinlets as indicated for unit A.

The outlet end (18) of microconduit I (17) may be directly connected toa downstream microcavity (20) of the kinds and functions indicated forunit A.

The relative dimensions of microconduit I (17) and the separationmicrocavity (4) including liquid inlets, outlets, vents, valves etc andtheir positions are preferably adapted for creating a driving plugheight in microconduit I as outlined for unit A.

The inventive aspect of unit E comprises also a microfluidic method forthe centrifugal fractionation of an aliquot of liquid containing denserand less dense material into a less dense upper phase and a denser lowerphase, and thereafter transporting at least a part of the upper phase todownstream parts of the same microchannel structure as in which theseparation is taking place. The method is in principle comprised withinthose variants of the method described for unit A which permitsufficient spinning to allow for centrifugal fractionation of the liquidin the upstream microcavity into a denser lower phase and a less denseupper phase without contaminating microconduit I with material thatafter the separation is in principle found exclusively in the lowerphase. The method aspect of unit D includes also further processing ofthe upper aliquot transported downstream, such as mixing for diluting,mixing with other aliquots comprising reactants, performing reactionssuch as biological reactions that are included in assay protocols likeenzyme assay protocols, affinity assay protocols etc. These assayprotocols may involve heterogenenous reactions such as in heterogeneousenzyme assays, heterogeneous non-competitive assays such as sandwichassays, heterogeneous competitive assay etc and the correspondinghomogeneous reactions and assay protocols. The assay protocols aretypically carried out for characterization of an uncharacterized entityin a sample, such as for the quantitative or qualitative determinationof the amount of an analyte.

F. Detection Unit.

Unit F is part of microchannel structure in which there is a detectionmicrocavity (49) which in the upstream direction is attached to an inletmicroconduit for transport of liquid (35) (transport microconduit) tothe detection microcavity (49). The detection microcavity is used fordetecting the result of a reaction taking place in the detectionmicrocavity or in a reaction microcavity (20) that is positionedupstream of the detection microcavity (49). Centrifugal force is usedfor transporting liquid between and through the microcavities. Thecharacterizing feature comprises that the detection microcavity (49)comprises a detection microconduit that has an inlet part (36) and anoutlet part (32) and therebetween an upward or a downward meander (39).

A meandering microconduit (39) is illustrated in FIG. 4. It comprises aplurality of consecutive returns (r₁, r₂, r₃, r₄, r₅, r₆, r₇, r₈ . . . )with an intermediary section (r₁₋₂, r₂₋₃, r₃₋₄, r₄₋₅, r₅₋₆, r₆₋₇, r₇₋₈ .. . ) between two neighbouring consecutive returns (r₁,r₂; r₂,r₃; r₃,r₄;r₄,r₅ . . . ) anywhere along the meander. The longitudinal position forthe returns and the intermediary sections is increasing in thelongitudinal direction of the meander (main flow direction of themeander) while the latitudinal position for the returns is alternatingaround a latitudinal center that may be common for the whole meander oronly for a part thereof that comprises two or more consecutive returns.The flow direction in every second intermediary section (=direction ofthe section) (r₁₋₂, r₃₋₄, r₅₋₆, r₇₋₈, . . . or r₂₋₃, r₄₋₅, r₆₋₇, r₈₋₉ .. . ) is either to the left or to the right while for every pair of twoconsecutive intermediary sections (r₁₋₂,r₂₋₃; r₂₋₃,r₃₋₄; r₃₋₄,r₄₋₅; . .. ) the flow direction in a first section is to the left or to the rightwhile the flow direction in the second section is the opposite(alternating lateral direction of the intermediary sections). Right andleft is relative to the main direction of the meander.

In centrifugal based systems downward and upward meanders means that themain direction of flow through the meander contains a component that istowards or along, respectively centrifugal force. In other words thefirst return is typically above the level of the last return for adownward meander and vice versa for an upward meander. A downward and anupward meander may in preferred cases be vertical by which is meant thatthe main direction of the meander (longitudinal direction) coincideswith the direction of centrifugal force. See FIG. 4 that illustrates avertical meander that is directed upwards.

At the priority date, typical meanders have a main flow direction thatfor upwards meanders form an angle γ with centrifugal force that is inthe interval 145°≦γ≦225° and for downwards meanders form an angle γwhich is in the interval −45°≦γ≦45°. With respect to vertically upwardand vertically downward meanders (γ is 180° and 0°, respectively), theupward one is preferred primarily because it more easily result incompact microchannel structures. Compare FIGS. 2 and 4.

In preferred variants the meander comprises two, three, four, five ormore returns. The upper limit may vary but typically the number ofreturns is ≦50, such as ≦25 or ≦10.

In typical innovative meander variants, each intermediary sectioncontains a stretch that is parallel with the corresponding stretch inone or more of the other sections. In preferred variants thisparallelism occurs for every second section, with absolute preferencefor every section as illustrated in figures and 4.

In upwardly directed meanders it may be advantageous when the heightposition (=longitudinal position) for every second return (r₁, r₃, r₅,r₇, . . . or r₂, r₄, r₆, r₈ . . . ) in consecutive returns (r₁, r₂, r₃,r₄, r₅, r₆, r₇, r₈ . . . ), such as for every consecutive return (r₁,r₂, r₃, r₄, r₅, r₆, r₇, r₈ . . . ), are increasing in the flowdirection. In downwardly directed meanders the height position isdecreasing in the flow direction for the corresponding combinations ofreturns. In the simplest of these variants the increase/decrease alongthe meander is constant between the first and second return in any pairof consecutive returns (r₁,r₂; r₂,r₃; r₃,r₄; r₄,r₅ . . . or between thefirst and third return in any triplets of consecutive returns (r₁,r₂,r₃;r₂,r₃,r₄; r₃,r₄,r₅ . . . ).

The detection microcavity (49) may comprise two or more serially linkedidentical or different forms of two or more meanders (not shown). Thusthe detection microconduit may comprise three, four or more meanderswith the downstream end of an upstream meander being in liquidcommunication with the upstream end of the closest downstream meanderpossibly. The liquid communication is via a linking microconduit part.The longitudinal direction of two meanders that are next to each othermay differ, for instance with one being downward and the other upward orthe other way round. One, two or more or all of the additional meandersin this kind of detection microcavity are typically downward or upward.

The detection microcavity (49) is typically associated with or capableof being associated with a sensor (not shown) that is capable ofdetecting a signal that represents the result of the reaction. Thesensor may be based on spectrometry, such as fluorometry,chemiluminometry (including biochemiluminometry, calorimetry,nephelometry, absorbance etc, calorimetry, conductonmetry etc. Thesensing principle utilized is typically matched with the materialbetween the inner wall of the detection microconduit and the outersurface of the device at the detection microcavity, for instance byconsisting of a material that is transparent or translucent for thesignal that is to be detected by a detector (sensor) associated with thedetection microcavity. This material may thus be translucent ortransparent for heat, and/or radiation in the UV-range, IR-range and/orthe visible range. The material can in many cases be a plastic material.

Upstream of the detection microcavity (49), such as between thedetection microcavity (49) and a reaction microcavity (20) in which thereaction to be monitored by measuring in the detection microcavity,there may be various functionalities for properly processing and/ortransporting liquids before entering the detection microcavity. Theremay thus be a) a routing function that prevents a liquid aliquot thatmight be harmful for the detection microcavity from passing through thedetection microcavity, b) a reaction chamber that comprises agents thatare capable of neutralizing or removing disturbing substances from aliquid, b) a stop/flow valve, c) flow restriction functionality thatimpedes liquid flow through the reaction microcavity etc. Thesedifferent kinds functionalities are well-known in the field and alsodescribed or referenced in this specification. The main function ofstop/flow valves and a flow restriction functionality in the innovativeunit is to secure proper reaction between reactants and/or othertreatments including transport between upstream parts of themicrochannel structure and the detection microcavity. Preferred valvesare non-closing valves, such as capillary valves. Flow restrictionfunctionalities include porous beds, membranes and the like placed inthe reaction microcavity. A narrow and/or long microconduit downstreamof the reaction microcavity may also work as a sufficient flowrestriction. Inner surfaces of a flow restriction functionality may in asimilar manner as a porous bed work as a solid phase for one or moreimmobilized reactants that are to be used in the desired reaction(s),for instance the inner surfaces of a restriction microconduit or of aporous bed, membrane, plug and the like. A solid phase of the kindsreferred to above is preferably a part of the reaction microcavity (20).

Non-closing valves, such as capillary valves are discussed underBackground Technology, General about Microfluidic Devices and thepublications referenced these parts of the specification. Various flowrestriction means or functionalities are given above and in WO 02075312(Gyros AB) and WO 03024598 (Gyros AB), among others.

A microcavity (20) upstream the detection microcavity may have variousgeometric forms. It may be an unbranched microconduit with no change incross-sectional dimension or an enlarged part (microcavity) of amicroconduit. It may be a mixing microcavity, reaction microcavity etcand contain one, two or more liquid inlets and allow for mixing of twoor more liquid aliquots of the same or different volumes within themicrocavity, including diluting. At least one of the aliquots containsone or more reactants to be used for the reaction(s) that takes place inthe reaction/detection microcavity (20/49). In the upstream directionevery liquid inlet of a microcavity (20) is directly or indirectlylinked to a liquid inlet arrangement comprising an inlet port, possiblywith an intervening volume-defining unit for one or more of themicroconduits in the inlet arrangement. See for instance WO 02074438(Gyros AB) and WO 03018198 (Gyros AB).

Unit F is typically present in a microchannel structure of amicrofluidic device that is capable of being spun about a spin axisthereby creating centrifugal force that can assist in moving liquidsthrough the detection microcavity from upstream parts of a microchannelstructure. The transport is typically primarily caused by centrifugalforce created by the spinning and/or by hydrostatic pressure built up inthe microchannel structure during spinning and/or by capillary force(self-suction). See General about Microfluidic Devices.

The inventive part of unit F also comprises a method comprisingdetecting in solution a result of a reaction that takes place in thedetection microcavity (49) and/or in a reaction microcavity (20) that isupstream of the detection microcavity and present in the samemicrochannel structure (2) as the detection microcavity (20). Thismethod comprises the steps of:

-   -   a) providing a microfluidic device comprising a microchannel        structure comprising unit F,    -   b) transporting a liquid I necessary for the detection into the        detection microcavity, said transporting comprises spinning of        the device to create centrifugal force that is used for the        transportation, and    -   c) detecting said result in the detection microcavity.        In preferred variants the reaction is part of a process protocol        comprising that a meander of the detection microcavity contains        liquid II prior to step (iii). Step (iii) then comprises that        liquid I displaces liquid II, typically without mixing with each        other.

General About Microfluidic Devices.

A microfluidic device is a device that comprises one, two or moremicrochannel structures in which one or more liquid aliquots in theμl-range, typically in the nanolitre (nl) range, containing variouskinds of reactants, such as analytes and reagents, products, samples,buffers and/or the like are processed. Each microchannel structurecomprises all the functionalities needed for performing the experimentthat is to be performed within the microfluidic device. A liquid aliquotin the μl-range has a volume ≦1 000 μl, such as ≦100 μl or ≦10 μl andincludes the nl-range that has an upper end of 5 000 nl but in mostcases relates to volumes ≦1 000 nl, such as ≦500 nl or ≦100 nl. Thenl-range includes the picolitre (pl) range. A microchannel structurecomprises one or more cavities and/or conduits that have across-sectional dimension that is ≦10³ μm, preferably ≦5×10² μm, such as≦10² μm.

A microchannel structure thus may comprise one, two, three or morefunctional parts selected amongst:

-   a) inlet arrangements comprising for instance one or more inlet    ports/inlet openings, possibly together with a volume-metering    microcavity,-   b) microconduits for liquid transport,-   c) reaction microcavities/units;-   d) mixing units, for instance comprising microcavities as discussed    elsewhere in this specification,-   e) units for microcavities for separating particulate matters from    liquids,-   f) units for separating dissolved or dispersed/suspended components    in the sample from each other, for instance by capillary    electrophoresis, chromatography and the like;-   g) detection microcavities/units;-   h) waste conduits/microcavities/units;-   i) valves;-   j) vents to ambient atmosphere;-   k) anti-wicking functions;-   l) liquid directing functions etc.    A functional part may have two or more functionalities:    -   1. a reaction microcavity and a detection microcavity may        coincide,    -   2. a volume-metering function may comprise one or more valve        functions and a metering microcavity and/or an anti-wicking        function,    -   3. a reaction microcavity may comprise one or more valve        functions and/or anti-wicking functions,    -   4. a passive valve function (capillary valve) based on a        non-wettable surface break may comprise also an anti-wicking        function etc.

Microcavities such as the upstream and downstream microcavitiesdiscussed in this specification including also reaction microcavities,separation microcavities, volume.-metering cavities, mixingmicrocavities, through-flow microcavities for instance associated withflow restriction means for controlling through flow, and other retainingliquid microcavities etc have volumes selected within the intervalsgiven above. Larger volumes such as ≧1 μl or ≧5 μl or ≧10 μl, but still≦1000 μl, such as ≦100 μl or ≦50 μl or ≦25 μl are typically contemplatedfor liquid samples containing an analyte before any concentration withina microchannel structure, diluents, and wash liquids. Thus largermicrocavities complying with these ranges are typically located to anupstream part of a microchannel structure and are typically present as avolume-metering microcavity, a separation microcavity for removing(separation) particulates from a sample containing an analyte, a mixingmicrocavities for diluting or mixing a sample containing an analyte witha diluent or a reagent, a diluent storing and/or metering microcavity, awash liquid storing and/or metering microcavity etc. Microcavitiesintended for retaining samples or liquid aliquots containing reagentstypically have smaller volumes, such as ≦5 μl or ≦1 μl or ≦0.5 μl or≦0.1 μl, i.e. in the nl-range.

Any of the microcavities discussed in the context of the innovativeunits, in Background Technology, this part of the specification, in WO03018198 (Gyros AB) (retaining microcavities) etc may in principle bepresent in a microchannel structure/unit of the innovative microfluidicdevices in direct or indirect fluid communication with the inlet end(16) or the outlet end (18) of microconduit I (17).

Various kinds of functional units in microfluidic devices have beendescribed by Gyros AB/Amersham Pharmacia Biotech AB: WO 9955827, WO9958245, WO 02074438, WO 0275312, WO 03018198, WO 03024598 etc and byTecan/Gamera Biosciences: WO 0187487, WO 0187486, WO 0079285, WO0078455, WO 0069560, WO 9807019, WO 9853311.

An inlet arrangement typically comprises an inlet port and at least onevolume-metering microcavity. There may be one separate inlet arrangementper microchannel structure. There may also be an inlet arrangement thatis common to all or a subset of the microchannel structures of thedevice. This latter arrangement typically comprises a common inlet portand a distribution manifold with one volume-metering microcavity foreach microchannel structure of the subset. See for instance WO 02074438(Gyros AB), WO 03018198 (Gyros AB), WO 03083108 (Gyros AB), WO2005094976 (Gyros AB) etc. A volume-metering microcavity istypicallycommunicating with downstream parts of the corresponding microchannelstructure, e.g. a mixing microcavity, reaction microcavity, separationmicrocavity etc. Microchannel structures linked together by a commoninlet arrangement and/or common distribution manifold define asubset/subgroup of the microchannel structures of the device.

Some inlet arrangements contains a microcavity that has novolume-defining ability but is solely used for initial storage of aliquid aliquot dispensed through an inlet port.

The abovementioned microcavities in inlet arrangements may have anU-shaped forms with lower part directed outwards from a spin axis andequipped with a liquid outlet to which is associated a valve function,typically a capillary valve. The liquid outlet is used for transport ofa dispensed aliquot to downstream parts of the microchannel structure towhich the inlet arrangement is associated. See for instance WO 0146465(Gyros AB).

A microcavity, such as a volume-metering microcavity, a mixingmicrocavity, a reaction microcavity etc typically has a valve or a flowrestriction means controlling the flow out of liquid from themicrocavity concerned. A valve at this position is typically passive,for instance utilizing a change in chemical surface characteristics atthe outlet end, such as a boundary between a hydrophilic and hydrophobicsurface (hydrophobic surface break) (WO 99058245 (Amersham PharmaciaBiotech AB)) and/or in geometric/physical surface characteristics (WO98007019 (Gamera)). See also WO 02074438 (Gyros AB), WO 04103890 (GyrosAB) and WO 04103891 (Gyros AB) for preferred valves that are based onhydrophobic surface breaks. Flow restriction means may be in the form ofporous beads, membranes and the like or in the form of relatively longan narrow microconduits (restriction microconduits). See for instance WO02075312 (Gyros AB) and WO 03024598.

See also WO 02075775 (Gyros AB) and WO 02075776 (Gyros AB).

The microfluidic device may also comprise other commonmicrochannels/microconduits that connect different microchannelstructures. Common channels/conduits including their various parts suchas inlet ports, outlet ports, vents, etc., are considered part of eachof the microchannel structures they are common for.

Each microchannel structure has at least one inlet opening for liquidsand at least one outlet opening for excess of air (vents) and possiblyalso for liquids.

The number of microchannel structures/device is typically ≧10, e.g. ≧25or ≧90 or ≧180 or ≧270 or ≧360. At least one, preferably two or more,such as all or a subset, of the microchannel structures on a devicecontain at least one of the innovative units presented in thisspecification.

A subgroup of microchannel structures comprises microchannel structureslinked together by a common functionality such as a common inletarrangement, which for instance is common for 4-25 microchannelstructures. All the microchannel structures of such a subgroup containessentially the identical unit(s) of the invention (selected from unitsA-F). Microchannel structures in such a subgroup are typicallyfunctionally equivalent, i.e. they can be used in a timely parallelfashion at least with respect to the occurring innovative unit(s).

Different principles may be utilized for transporting the liquid withinthe microfluidic device/microchannel structures between two or more ofthe functional parts described above.

Inertia force may be used, for instance by spinning the disc asdiscussed in the subsequent paragraph. Other useful forces areelectrokinetic forces, non-electrokinetic forces such as capillaryforces, hydrostatic pressure etc.

A microfluidic device typically is in the form of a disc. The preferredformats have an axis of symmetry (Ce) that is perpendicular to orcoincides with the disc plane. In the former case n is an integer ≧2, 3,4 or 5, preferably ∞ (C_(∞)). In the latter case n is typically 2. Inother words the disc may be rectangular, such as in the form of asquare, or have other polygonal forms. It may also be circular. Once theproper disc format has been selected centrifugal force may be used fordriving liquid flow, e.g. by spinning the device about a spin axis thattypically is perpendicular to or parallel with the disc plane. Parallelin this context includes that the spin axis coincides with the discplane. In the most obvious variants at the priority date, the spin axiscoincides with the above-mentioned axis of symmetry. Preferred variantsin which the spin axis is not perpendicular to the disc plane are givenin International Patent Application WO 04050247 (Gyros AB)

For preferred centrifugal-based variants, each microchannel structurecomprises an upstream section that is at a shorter radial distance thana downstream section relative to the spin axis. Spinning of the deviceabout this spin axis will then induce transportation of liquid from theupstream section to the downstream section, for instance throughmicroconduit I of units A-E or into the meander of unit F.

The preferred devices are typically disc-shaped with sizes and formssimilar to the conventional CD-format, e.g. sizes that correspondsCD-radii that are the interval 10%-300% of the conventional CD-radii(about 12 cm). The upper and/or lower sides of the disc may or may notbe planar.

Microchannel structures or parts thereof such as microconduit I of unitsA-E or the meander of unit F are preferably manufactured from anessentially planar substrate surface that exhibits uncoveredmicrostructures defining at least a part of microconduit I of units A-Eor at least part of the meander of unit F and another essentially planarsubstrate surface exhibiting the remaining part of microconduit I or theremaining part of the meander. The covered form of microconduit I or apart thereof or of the meander or a part thereof is obtained by apposingthe two substrate surfaces defining the desired structure together.Compare for instance WO 91016966 (Pharmacia Biotech AB), WO 01054810(Gyros AB), WO 4050247 (Gyros AB), WO 03055790 (Gyros AB etc. Bothsubstrates are preferably fabricated from plastic material, e.g. plasticpolymeric material.

The fouling activity and hydrophilicity of inner surfaces should bebalanced in relation to the application. See for instance WO 0147637(Gyros AB) and WO 03086960 (Gyros AB).

The terms “wettable” and “non-wettable” with respect to inner wallscontemplate that the inner surface of an inner wall has a water contactangle ≦90° or ≧90°, respectively. In order to facilitate efficienttransport of a liquid between different functional parts, inner surfacesof the individual parts should primarily be wettable, preferably with acontact angle ≦60° such as ≦50° or ≦40° or ≦30° or ≦20°. Thesewettability values apply for at least one, two, three or four of theinner walls of a microconduit. In the case one or more of the innerwalls have a higher water contact angle, for instance by beingessentially non-wettable, this can be compensated for by a lower watercontact angle for the other inner wall(s). The wettability, inparticular in inlet arrangements, should be adapted such that an aqueousliquid will be able to fill up an intended microcavity/microconduit bycapillarity (self suction) once the liquid has started to enter thecavity, typically with the inner surfaces being in a dry state. Ahydrophilic inner surface in a microchannel structure may comprise oneor more local hydrophobic surface breaks in a hydrophilic inner wall,for instance as part of a passive valve, an anti-wicking function, avent solely functioning as a vent to ambient atmosphere etc. See also WO99058245 (Gyros AB) and WO 02074438 (Gyros AB), and WO 04103890 (GyrosAB) and WO 04103891 (Gyros AB) for preferred hydrophobic surface breaks.

Liquids that are processed with the innovative microfluidic devices,microchannels structures and units are typically aqueous containingwater mixed with a water-miscible solvent that may contain one, two ormore water-miscible or water immiscible organic solvents such as loweralcohols (methanol, ethanol, isopropanol, n-propanol, a butanol, apentanol, etc, ethylene glycol, glycerol and other liquid polyalcoholsetc), N,N-dimethyl formamide, dimethyl sulfoxide, acrylonitril, dioxin,lower alkyl polyethers such as dioxane, dimethoxy ethylene etc. Due careis taken in combining plastic material with liquid to be processed suchthat device is not dissolved, deformed or otherwise broken by the liquidto be processed.

The innovative units, microchannel structures, and microfluidic devicescan be used for assays with life sciences, such as receptor-ligandassays like immuno assays, nucleic acid assays, etc, enzyme assays, cellbased assays etc. Typical variants of these kinds of assays aredescribed in WO 9955827, WO 0040750, WO 02075312, WO 03093802, WO2004083108, WO 2004083109, WO 2004106926, WO 2006009506,PCT/SE2005/001887 (corresponding U.S. Ser. No. 11/______ filed Dec. 12,2006 “Microfluidic Assays and Microfluidic Devices”), PCT/SE2006/000071,PCT/SE2006/000072 etc (all of Gyros AB/Gyros Patent AB) which are herebyincorporated by reference in their entirety.

EXPERIMENTAL PART The Device Used

The drawings illustrate a microchannel structure comprising allfunctions of units A-F. The structure has been used for the collectionof plasma from whole blood.

FIG. 1 shows the microfluidic device in which the actual experimentspresented below have been carried out.

FIG. 2 is an enlarged view of one of the microchannel structures.

FIG. 3 shows an enlarged view of the key part of unit C.

FIG. 4 is the lower part of the structure shown in FIG. 2. The figurefocuses on unit F.

The natural size of the device (1) shown in FIG. 1 is the same as aconventional CD having a diameter of 12 cm. From the sizes in FIG. 1 thewidth of the different parts of the microchannel structures can beconcluded bearing in mind that the true diameter is 12 cm. The depth ofthe various parts is as a rule 100 μm but may in certain positions beshallower (e.g dual depths/barriers for retaining solid phases in theform of beds of packed particles (columns) (33), microchannels (42) invalve I (24) etc). The device (1) has 27 microchannel structures (2).The device is intended to be spun around a spin axis that passes throughthe center (3) of the device.

The structure comprises an upstream microcavity I (4 a+b) with a liquidinlet I (5) at the top (7)a, a liquid outlet I (6) at an intermediarylevel between the top (7) and the bottom (8) dividing the upstreammicrocavity in an upper part (4 a) and a lower part (4 b). An inletmicroconduit (8 a) is connected to the liquid inlet I (5) at the top (7)of the upstream microcavity. The inlet microconduit (8 a) starts in aninlet port (9) (═Opening in the surface of the device) that is above thelevel of the top (7) of the upstream microcavity (4 a+b). At the samelevel as the liquid inlet I (5) there is an overflow opening (10) in theinlet microconduit (8 a) The overflow opening (10) is connected to adownwardly directed overflow microconduit (11) that brings added excessof liquid (above the overflow opening) down into an overflow microcavity(11 a) that vents (13) to the surface of the device (1). Thelower/downstream part (4 b) of the upstream microcavity (4 a+b) dividesinto two U-shaped finger microconduits (4 b) below the level of liquidoutlet I (6). The downward part of each finger microconduitnarrows/tapers (with angle β) before turning upwards (12). Each of theupward parts (12) ends in a vent opening (14) in the surface of thedevice (1) at a level above the level of liquid inlet I (5). The designwith U-shaped and tapered finger microconduits is believed to minimizeenclosure of air bubbles during filling of the upstream microcavity (4a+b). Valves/vents in the form non-wettable surface areas (15 a) (e.g.as finger vents unit C) may be placed in the finger microconduit tominimize the risk for leakage of liquid through the vent openings(13,14) in the surface of the device (1). If these valves/vents areplaced below the level of liquid outlet I (6) they are likely to give amore controllable volume-metering in the upper part (4 b) of theupstream microcavity (4 a+b) and the vent openings (13,14) could also beplaced at a lower level than the inlet port (9) and the overflow opening(10) liquid inlet I (5). A non-wettable surface area (15 b) (valve) mayfor similar reasons be placed in the overflow microconduit (11), such asat its connection to the overflow microcavity (11 a).

Liquid outlet I (6) of the upstream microcavity is connected to theinlet end (16) of microconduit I (17) that ends in an outlet end (18)that is well below the level of the inlet end (16) of the microconduit(level of liquid outlet I (6)). In the structure shown, this outlet end(18) is part of a branching or intersection involving a flow pathstarting at a liquid inlet function (19) of a downstream microcavity II(20) and ending at a liquid inlet II (21) of this downstream microcavityII (20). The inlet end (16) of microconduit I (17) is at a higher levelthan the outlet end (18) and has an upward turn with an upper extreme(22). In the upward section (23 a) of microconduit I (17) there is acapillary valve I (24) that preferably is a finger valve (unit C) of thetype shown in FIG. 3. By varying the position of capillary valve I (24)in microconduit I (17) during the manufacturing of the device, inparticular in its upward section (23 a), the spin speed required forbreak through can easily be varied. By adding an extra capillary valveI′ (25) (typically as a non-wettable surface break) downstream ofcapillary valve I (24) advantages as discussed in the specification willbe achievable. By placing the upper extreme (22) at a level above thelevel of the top (7) of the upstream microcavity (4 a+b) and capillaryvalve I (24) at a level below the level of the top (7) there areadvantages to gain in the separation of denser material from less densematerial in a lower and an upper phase, respectively, as discussedelsewhere in the specification.

The downstream microcavity II (20) may as illustrated in the drawingshave a number of liquid inlets II′, II″, II′″ (25 a,26,27) in additionto liquid inlet II (21). Some of them (25 a,27) may contain avolume-defining unit containing an overflow microconduit (28,29) endingin an overflow microcavity (30,31). In association with liquid outlet II(32) of the downstream microcavity there may be a capillary valve or asin the structure shown means (33,34) for controlling material transportout of the microcavity (20). Thus there may be a barrier (33)constricting the lower part of the microcavity (20) for collectingparticles in the form of a particulate solid phase as a packed bed (34)against the barrier (33).

Downstream of the downstream microcavity II (20) there may be atransport microconduit (35) leading to a detection microcavity that isas defined for unit F of the present invention, i.e. the detectionmicrocavity comprises an inlet part (36), an outlet part (37) and amicroconduit (39) that defines a meander. As shown in the drawings themeander may have a vertically upward direction (40), i.e. thelongitudinal direction of the meander and also the mean flow directionin the meander are in practice fully in the opposite direction to thecentrifugal force (41) applied to move the liquid upstream in themeander. The meander has a number of consecutive returns (r₁, r₂, r₃,r₄, r₅, r₆, r₇, r₈ . . . ). Within each pair of neighbouring returns(r₁,r₂; r₂,r₃; r₃,r₄; r₄,r₅ . . . ) there is an intermediary section(r₁₋₂, r₂₋₃, r₃₋₇, r₄₋₅, r₅₋₆, r₆₋₇, r₇₋₈ . . . ) that for preferredvariants show parallelism for every second section (r₁₋₂, r₃₋₄, . . . )such as for every section (r₁₋₂, r₂₋₃, r₃₋₄, r₄₋₅ . . . ).

The device was manufactured by attaching a lid to a bottom substrate inwhich the microchannel structures had been replicated by injectionmoulding (WO 01054810 (Gyros AB)). Before attaching the lid, the surfacehad been plasma treated (WO 0056808 (Gyros AB)) and local non-wettablesurface areas introduced (WO 99058245, WO 04103891 (Gyros AB)). Theinner surfaces was subsequently coated with a non-ionic hydrophilicpolymer (WO 01047637 (Gyros AB)).

EXPERIMENTAL Variant A

A microchannel structure (2) containing a separation microcavity (4 a+b)(unit E) was used to separate whole blood into cell free plasma. Wholeblood was filled into the structure via inlet port (9) to a level abovethe overflow opening (10). After separation the plasma was delivereddown to the column (34) through microconduit I (17) containing a fingervalve (24) (units Units A-C) in which the local non-wettable surface(44) fully covers the microchannels (42) of the finger valve (24).During filling of the separation microcavity (4 a+b) the front meniscusof the blood will stop at the downstream end of valve I (24).

To separate the blood the following spin sequence was used: (i) 1000 rpm30 s, (ii) 1500 rpm 180 s, (iii) 4000 rpm 4 s, (iv) 2000 rpm 10 s

Steps (i) and (ii) were used to separate the red and white cells fromthe plasma where the first step also defined the blood volume byactivating the overflow microconduit (11). Step (iii) was used toactivate the transport of the cell free plasma through capillary valve(24) in microconduit I (17), over the upper extreme (22) and down to thedownstream microcavity (reaction microcavity) (20) and to the column(34) and finally step (iv) was used to empty the upper part (plasmachamber) (4 b) of the upstream microcavity (4 a+b). The cell free plasmawas then spun through the column for further processing.

Variant B

If the local non-wettable surface area (44 b) is placed across the lowerends (45) or within the of the fingers/micro channels (42) the upperends (43) of the fingers will be left fully hydrophilic and prone tocapillary transport once a liquid front has passed the localnon-wettable surface area of the valve. This positioning of thenon-wettability permits higher spin speeds and G-forces during theactual separation step (into two phases) and thus also more efficientseparations. For instance: (i) 2000 rpm 10 s, (ii) 4000 rpm 50 s, (iii)9000 rpm 15 s, (iv) 0 rpm 15 s, (v) 2000 rpm 10 s. The spin speeds 2000to 9000 rpm are used to separate the blood into a plasma fraction and acell-fraction. At 9000 rpm the plasma breaks the hydrophobic barrier ofthe valve (24). However, the plasma does not enter the drainage channeluntil the spin rate is lowered to zero and the capillary force drag ininto the drainage channel (downstream/downward section of microconduit I(17)). When the spin rate then increases to 2000 rpm the liquid that hasfilled the drainage channel will form a driving plug, which will help toempty the plasma chamber.

General Statement

Certain innovative aspects of the invention are defined in more detailin the appending claims. Although the present invention and itsadvantages have been described in detail, it should be understood thatvarious changes, substitutions and alterations can be made hereinwithout departing from the spirit and scope of the invention as definedby the appended claims. Moreover, the scope of the present applicationis not intended to be limited to the particular embodiments of theprocess, machine, manufacture, composition of matter, means, methods andsteps described in the specification. As one of ordinary skill in theart will readily appreciate from the disclosure of the presentinvention, processes, machines, manufacture, compositions of matter,means, methods, or steps, presently existing or later to be developedthat perform substantially the same function or achieve substantiallythe same result as the corresponding embodiments described herein may beutilized according to the present invention. Accordingly, the appendedclaims are intended to include within their scope such processes,machines, manufacture, compositions of matter, means, methods, or steps.

1. A microfluidic device A) comprising a hydrophilic microchannelstructure in which there is a functional unit that comprises: anupstream microcavity I with a liquid outlet I and capable of retaining apredetermined liquid volume (aliquot) defining an upper liquid level Iin the microcavity, a microconduit I that has an inlet end and an outletend, the inlet end being connected to liquid outlet I, and a capillaryvalve I that is associated with microconduit I, and B) being capable ofspinning about a spin axis to create centrifugal force that can assistin transporting liquid from said upstream microcavity into and/orthrough microconduit I, characterized in that (i) the inlet end iscloser to the spin axis than the outlet end, (ii) valve I is positioneda) at liquid outlet I, or b) between the inlet end and the outlet end,and (iii) the difference in radial distance between the inlet end andthe outlet end of microconduit I (the inlet end coincides with liquidoutlet I) is typically ≧5%, such as ≧10% or ≧50% or ≧100% or ≧200% or≧500%, of the difference in radial distance between the uppermost partof the upstream microcavity and liquid outlet I liquid outlet Icoincides with the inlet end of microconduit I).
 2. The device of claim1, characterized in that the part of microconduit I that is downstreamof valve I is capable of transporting liquid passing through valve I asa continuous liquid plug extending from valve I and ending downstream ina front meniscuses within microconduit I or at the outlet end.
 3. Thedevice of claim 1, characterized in that microconduit I comprises asection, which (a) is downstream of valve I and (b) has across-sectional area that is smaller than the cross-sectional areabetween the inlet end of microconduit I and valve I, for instance with afactor ≦1, such as ≦0.5 or ≦0.2 or ≦0.1.
 4. The device of claim 1characterized in that valve I is placed in microconduit I.
 5. The deviceof claim 1, characterized in that microconduit I comprises an upwardturn that comprises an upper extreme that is at or above the level ofthe inlet end of microconduit I.
 6. The device of claim 5, characterizedin that said upper extreme is i) above the level of upper liquid levelI, such as above the level of the uppermost part of the upstreammicrocavity, or ii) at an intermediary level between the level of liquidoutlet I and the level of the uppermost part of the upstreammicrocavity, such as below the level of upper liquid level I of theupstream microcavity, or iii) at the same level as the inlet end ofmicroconduit I, preferably at the same level as the inlet end/liquidoutlet.
 7. The device of claim 5, characterized in that valve I isupstream or, downstream of or at said extreme, e.g. at a level that islower than the uppermost part of the upstream microcavity, such as lowerthan upper liquid level I.
 8. The device of claim 1, characterized inthat a) liquid outlet I divides the upstream microcavity in a lower partthat is below the level of liquid outlet I and an upper part that isabove the level of liquid outlet I, and b) the lower partconstitutes >0%, such as ≧10%, or ≧25% or ≧50% or ≧70% or ≧80% of thetotal volume of the upstream microcavity.
 9. The device of claim 1,characterized in that the outlet end of microconduit I is linked to theliquid inlet II of a downstream microcavity II which comprises: a) oneor more vent functions, and/or b) one or more additional liquid inletsII′, II″ . . . , at least one of which possibly coincides with one ofsaid vent functions, and/or c) one or more liquid outlets II, II′, II″ .. . at least one of which possibly coincides with one of said ventfunctions, and/or is/are at a lower level than the level(s) of one, two,three or more of said liquid inlets II, II′, II″ . . . , and/or d) acapillary valve and/or a restriction means for each of at least one ofsaid one or more liquid outlets II, II′, II′ . . . , which valve and/ormeans is capable of controlling the transport of material through theliquid outlet.
 10. The device of claim 9, characterized in that A) theoutlet downstream microcavity comprises liquid outlet II, and B) theradial distance between the inlet end and the outlet end of themicroconduit radial distance between liquid outlet I and liquid inletII) is ≧100% or ≧200% or ≧500% or ≧1000%, of a) the radial distancebetween the level of liquid inlet II and the level of the lowest of thecapillary valves in the liquid outlets of the downstream microcavity, orb) the radial distance between upper liquid level II in the downstreammicrocavity and the level of the lowest of the capillary valves in theliquid outlets of the downstream microcavity.
 11. The device of claim 1,characterized in that the upstream microcavity is constricted at thelevel liquid outlet I for instance by at least one, two or more of theinner walls of one or both of these microcavities forming an acute anglewith a straight line (radius) going from spin axis towards theconstriction, for instance with said angle being in the interval of10°-50°, such as 20°-40° and preferably 25°-35°.
 12. The device of claim9, characterized in that said microchannel structure comprises at leasttwo of said functional unit, such that the downstream microcavity of anupstream unit is in liquid communication with the upstream microcavityof the closest downstream unit, a) said units being equal or different,b) a downstream microcavity of an upstream unit possibly being theupstream microcavity of the closest downstream unit, and/or c) otherfunctional units possibly being inserted between the units.
 13. Thedevice of claim 1, characterized in that valve I is a finger valve, forinstance as defined for unit C, and that different parts of microconduitI may be designed as and contain or being directly or indirectly linkedto functionalities as described for units A-F of the specification. 14.The device of claim 1, characterized in that valve I and possibly one ormore of the valves associated with liquid outlets of the downstreammicrocavity, if present, are capillary valves, for instance based on thepresence of local non-wettable surface area.
 15. The device of claim 1,characterized in that different parts of microconduit I may be designedas and contain or being directly or indirectly linked to functionalitiesas described for units A-F of the specification.